Polymorphisms in the SOCS7 gene and glucose homeostasis traits

BACKGROUND: SOCS7 is a member of the suppressor of cytokine signaling family of proteins and is expressed in skeletal muscle and islets. SOCS7 deficient mice develop islet hyperplasia in the setting of increased insulin sensitivity and normal glucose tolerance. The objective of this study was to determine if variants in SOCS7 play a role in variation of glucose and insulin levels and the development of type 2 diabetes (T2DM). RESULTS: Five SOCS7 tagging SNPs were genotyped in diabetic and nondiabetic Old Order Amish. A case–control study was performed in T2DM (n = 145) and normal glucose tolerant (n = 358) subjects. Nominal associations were observed with T2DM and the minor alleles for rs8068600 (P = 0.01) and rs8074124 (P = 0.04); however, only rs8068600 remained significant after Bonferroni adjustment for multiple comparisons (P = 0.01). Among nondiabetic Amish (n = 765), no significant associations with glucose or insulin traits including fasting or 2 hour glucose and insulin from the oral glucose tolerance test, insulin or glucose area under the curve, Matsuda Index or HOMA-IR were found for any of the SNPs. CONCLUSION: In conclusion, genetic variants in the SOCS7 gene do not impact variation in glucose homeostasis traits and only minimally impact risk of T2DM in the Old Order Amish. Our study was not able to address whether rare variants that potentially impact gene function might influence T2DM risk

Analysis of coding variants in the betacellulin gene in type 2 diabetes and insulin secretion in African American subjects

BACKGROUND: Betacellulin is a member of the epidermal growth factor family, expressed at the highest levels predominantly in the pancreas and thought to be involved in islet neogenesis and regeneration. Nonsynonymous coding variants were reported to be associated with type 2 diabetes in African American subjects. We tested the hypotheses that these previously identified variants were associated with type 2 diabetes in African Americans ascertained in Arkansas and that they altered insulin secretion in glucose tolerant African American subjects. METHODS: We typed three variants, exon1 Cys7Gly (C7G), exon 2 Leu44Phe (L44F), and exon 4 Leu124Met (L124M), in 188 control subjects and 364 subjects with type 2 diabetes. We tested for altered insulin secretion in 107 subjects who had undergone intravenous glucose tolerance tests to assess insulin sensitivity and insulin secretion. RESULTS: No variant was associated with type 2 diabetes, and no variant altered insulin secretion or insulin sensitivity. However, an effect on lipids was observed for all 3 variants, and variant L124M was associated with obesity measures. CONCLUSION: We were unable to confirm a role for nonsynonymous variants of betacellulin in the propensity to type 2 diabetes or to impaired insulin secretion

Variations in the G6PC2/ABCB11 genomic region are associated with fasting glucose levels

Identifying the genetic variants that regulate fasting glucose concentrations may further our understanding of the pathogenesis of diabetes. We therefore investigated the association of fasting glucose levels with SNPs in 2 genome-wide scans including a total of 5,088 nondiabetic individuals from Finland and Sardinia. We found a significant association between the SNP rs563694 and fasting glucose concentrations (P = 3.5 × 10–7). This association was further investigated in an additional 18,436 nondiabetic individuals of mixed European descent from 7 different studies. The combined P value for association in these follow-up samples was 6.9 × 10–26, and combining results from all studies resulted in an overall P value for association of 6.4 × 10–33. Across these studies, fasting glucose concentrations increased 0.01–0.16 mM with each copy of the major allele, accounting for approximately 1% of the total variation in fasting glucose. The rs563694 SNP is located between the genes glucose-6-phosphatase catalytic subunit 2 (G6PC2) and ATP-binding cassette, subfamily B (MDR/TAP), member 11 (ABCB11). Our results in combination with data reported in the literature suggest that G6PC2, a glucose-6-phosphatase almost exclusively expressed in pancreatic islet cells, may underlie variation in fasting glucose, though it is possible that ABCB11, which is expressed primarily in liver, may also contribute to such variation

A Central Role for GRB10 in Regulation of Islet Function in Man

Peer reviewe

Thyroid Storm with Multiorgan Failure Treated with Plasmapheresis

Background. Thyroid storm is a severe manifestation of thyrotoxicosis and can present with multiorgan failure. First line treatment of thyroid storm is directed towards decreasing thyroid hormone production and peripheral conversion of T4 to T3, and treating adrenergic symptoms. When medical therapy fails, plasmapheresis is an alternative treatment option. Here we present a patient with thyroid storm and multiorgan failure who was treated with plasmapheresis. Case. A 50-year-old male with a history of hyperthyroidism, hypertension, and congestive heart failure presented to another hospital with fever and altered mentation. He was found to have pneumonia on imaging and was started on antibiotics. He developed shock complicated by atrial fibrillation with rapid ventricular rate which was treated with amiodarone. He was transferred to our hospital for further management. On arrival, TSH was 7 ng/dL and total T3 was 358 ng/dL. The endocrinology team determined he was in thyroid storm. His medical treatment of thyroid storm was aggressively titrated to maximal therapy. His hospital course was complicated by transaminitis, respiratory failure requiring intubation, shock requiring vasopressor support, kidney failure requiring continuous renal replacement therapy, and heart failure. Despite maximal anti-thyroid therapy, he had not improved clinically and T4 and T3 remained markedly elevated. A 4-day course of plasmapheresis was initiated resulting in marked lowering of T4 and T3 and clinical stability. Conclusion. While current guidelines for plasmapheresis for thyroid storm recommend individualized decision making, no further clarification is provided on who would be a good candidate for the procedure. We present a patient with thyroid storm and multiorgan failure who was treated with plasmapheresis after failing maximal medical therapy. Given the significant improvement seen with plasmapheresis, endocrinologists should consider this mode of treatment earlier in the course of thyroid storm when patients are not improving with medical therapy alone

No effect of the Trp64Arg β3-adrenoceptor gene variant on weight loss, body composition, or energy expenditure in obese, Caucasian postmenopausal women

The Trp64Arg polymorphism in the β3-adrenoceptor gene has been associated with increased prevalence of obesity, type 2 diabetes, and low rates of energy expenditure, although these findings are not unanimous. It is currently unknown if the presence of the Trp64Arg gene variant impedes the loss of body weight in obese, postmenopausal women via a reducing effect on energy expenditure. The objective of this study was to compare body composition and energy expenditure in carriers and noncarriers of the Trp64Arg variant in the β3-adrenoceptor before and after weight loss. We measured body composition, total daily energy expenditure (TEE), resting metabolic rate (RMR), physical activity energy expenditure (PAEE), thermic effect of feeding (TEF), and respiratory quotient (RQ) in 34 obese, postmenopausal women (19 carriers and 15 noncarriers for the Trp64Arg variant) before and after a weight loss intervention. There were no differences in body composition or daily energy expenditure and its components between the 2 groups at baseline. There were significant reductions in body mass, body mass index (BMI), percent body fat, fat-free mass, and fat mass (main effect, all P \u3c .0001) when analyzed with the 2 genotypes combined, but no significant differences between carriers and noncarriers with respect to change in these variables (group × time interaction term, all P \u3e .05). Total energy expenditure tended to be reduced (490 kJ.d-1, P = .13) in both groups following weight loss, but there was no significant group × time interaction term (P = .78), indicating no difference in the response of the 2 genotypes. There was a 9% reduction in RMR (611 kJ.d-1, P \u3c .001) when both groups were considered together, but no significant group × time interaction term (P = .84), suggesting that both groups responded in a similar manner to the weight loss intervention. PAEE and the TEF were not different following weight loss (both P \u3e .60). There was a trend for RQ to be reduced after weight loss (P = .07), but there was no difference between carriers or noncarriers of the Trp64Arg variant (P = .58). In summary, we found that obese postmenopausal women who carry the Trp64Arg variant in the β3-adrenoceptor had similar changes in body composition and energy expenditure to noncarriers of the variant in response to prolonged caloric restriction. These results suggest that the presence of the Trp64Arg variant in the β3-adrenoceptor should not be a hindrance to weight reduction. Copyright 2002, Elsevier Science (USA). All rights reserved

The Exon 1 Cys7Gly Polymorphism Within the Betacellulin Gene Is Associated With Type 2 Diabetes in African Americans

In vitro and in vivo studies suggest a role for betacellulin in islet neogenesis and regeneration. Since abnormalities in β-cell function play a role in the development of type 2 diabetes, a mutation in the betacellulin gene could potentially contribute to the development of type 2 diabetes. Using RT-PCR, we initially determined that betacellulin was expressed in 9- to 24-week-old human fetal pancreas. We then screened the betacellulin gene for mutations in subjects with type 2 diabetes and identified seven polymorphisms in segments encompassing the 5′ untranslated region (G-233C, A-226G), exon 1 (T̅GC19G̅GC, Cys7Gly), exon 2 (C̅TC130T̅TC, Leu44Phe), exon 4 (T̅TG370A̅TG, Leu124Met), intron 2 (T-31C), and intron 4 (C-4T). These polymorphisms were genotyped in an expanded set of diabetic case and control subjects. Among African Americans (n = 334), the frequency of the Gly7 allele in exon 1 was 31.9% in diabetic case subjects compared with 45.1% in nondiabetic control subjects (P = 0.0004). Allele frequencies for the other polymorphisms did not differ significantly between African-American case and control subjects. Additionally, there were no significant differences in allele frequencies between case and control subjects among the Caucasian sample (n = 426) for any of the seven polymorphisms, including the Gly7 variant. Further studies will be needed to understand the different roles that betacellulin polymorphisms play in susceptibility to type 2 diabetes in Caucasians and African Americans

Association of a polymorphism in the betacellulin gene with type 1 diabetes mellitus in two populations

Betacellulin, a member of the epidermal growth factor family, is expressed in fetal and adult pancreas. In vitro and in vivo studies suggest a role for betacellulin in islet neogenesis and regeneration. Therefore, a mutation in the betacellulin gene might lead to fewer beta cells. With reduced beta cell reserve, beta cells may not be able to compensate for an autoimmune attack, and in turn, susceptibility to type 1 diabetes mellitus (T1DM) would increase. Previous mutational analysis identified seven polymorphisms in the betacellulin gene [5' UT (-233G>C, -226A>G), exon 1 (TGC19GGC, Cys7Gly), exon 2 (CTC130TTC, Leu44Phe), exon 4 (TTG370ATG, Leu124Met), intron 2 (-31T>C), and intron 4 (-4C>T)]. An association study of these variants with T1DM was first carried out in 100 Caucasian subjects with T1DM and 282 Caucasian subjects without diabetes recruited at the University of Maryland. The frequency of the intron 4 T-4 allele was significantly higher among nondiabetic controls than that among diabetic cases (0.29 vs 0.21, p=0.04). Allele frequencies for the other polymorphisms did not differ significantly between cases and controls. The intron 4 T-4 association was then replicated by transmission disequilibrium testing in a separate population of Caucasian parent/offspring with T1DM trios (n=168 trios, 113 informative) recruited at the Medical College of Wisconsin (p=0.024). An interaction of the intron 4 T-4 allele and human leukocyte antigen (HLA) was also detected with undertransmission of the T allele in those T1DM subjects with susceptible HLA types as compared to those T1DM subjects without susceptible HLA types (p=0.018). RNA studies of the intron T-4 variant showed similar RNA levels for intron 4 T-4 and intron 4 C-4 alleles. Additionally, there was no evidence for an effect of this variant on exon-intron splicing. We conclude that the intron 4 T-4 allele in the betacellulin gene is associated with lower risk of T1DM and may interact with HLA. Further studies will be necessary to establish the significance of this association