TCF7L2 polymorphisms are associated with amygdalar volume in elderly individuals with Type 2 Diabetes

The association between several Single Nucleotide Polymorphisms (SNPs) within the transcription factor 7-like 2 (TCF7L2) gene and Type 2 Diabetes (T2D) as well as additional T2D-related traits is well established. Since alteration in total and regional brain volumes are consistent findings among T2D individuals, we studied the association of four T2D susceptibility SNPS within TCF7L2 (rs7901695, rs7903146, rs11196205, and rs12255372) with volumes of white matter hyperintensities (WMH), gray matter, and regional volumes of amygdala and hippocampus obtained from structural MRI among 191 T2D elderly Jewish individuals. Under recessive genetic model (controlling for age, sex and intracranial volume), we found that for all four SNPs, carriers of two copies of the T2D risk allele (homozygous genotype) had significantly smaller amygdalar volume: rs7901695- CC genotype vs. CT + TT genotypes, p = 0.002; rs7903146-TT vs. TC + CC, p = 0.003; rs11196205- CC vs. CG + GG, p = 0.0003; and rs12255372- TT vs. TG + GG, p = 0.003. Adjusting also for T2D-related covariates, body mass index (BMI), and ancestry did not change the results substantively (rs7901695, p = 0.003; rs7903146, p = 0.005; rs11196205, p = 0.001; and rs12255372, p = 0.005). Conditional analysis demonstrated that only rs11196205 was independently associated with amygdalar volume at a significant level. Separate analysis of left and right amygdala revealed stronger results for left amygdalar volume. Taken together, we report association of TCF7L2 SNPs with amygdalar volume among T2D elderly Jewish patients. Further studies in other populations are required to support these findings and reach more definitive conclusions.

Amygdalar Volume in Borderline Personality Disorder With and Without Comorbid Post-traumatic Stress Disorder: A Meta-analysis

IntroductionFour studies have found a smaller amygdalar volume in patients with borderline personality disorder (BPD) relative to controls, whereas four other studies have found similar amygdalar volume in BPD patients relative to controls. This study aims to compare amygdalar volumes of BPD patients with controls, and also to compare BPD patients with and without post-traumatic stress disorder (PTSD) with controls in order to determine whether PTSD can explain the heterogeneity of findings.MethodSystematic review and meta-analysis of magnetic resonance imaging studies that measured amygdalar volumes in BPD patients and healthy controls.FindingsA significant reduction of amygdalar volumes in BPD patients was confirmed (p < .001). However, data from the studies that discriminated BPD patients with and without PTSD indicated that amygdalar volumes were significantly smaller in BPD patients without PTSD relative to controls (left: p = .02; right: p = .05), but not in BPD patients with PTSD relative to controls (left: p = .08; right: p = .20).ConclusionThis meta-analysis suggests that amygdalar volumes are reduced in patients with BPD. This pattern is confirmed in BPD patients without PTSD, but not in BPD patients with PTSD, raising the possibility that reduced amygdalar volume in BPD patients cannot be explained by comorbid PTSD.