A proportion of angiotensin II type 1 receptor blockers (ARBs) improves glucose dyshomeostasis and insulin resistance in a clinical setting. Of these ARBs, telmisartan has the unique property of being a partial agonist for peroxisome proliferator-activated receptor γ (PPARγ). However, the detailed mechanism of how telmisartan acts on PPARγ and exerts its insulin-sensitizing effect is poorly understood. In this context, we investigated the agonistic activity of a variety of clinically available ARBs on PPARγ using isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) system. Based on physicochemical data, we then reevaluated the metabolically beneficial effects of telmisartan in cultured murine adipocytes. ITC and SPR assays demonstrated that telmisartan exhibited the highest affinity of the ARBs tested. Distribution coefficient and parallel artificial membrane permeability assays were used to assess lipophilicity and cell permeability, for which telmisartan exhibited the highest levels of both. We next examined the effect of each ARB on insulin-mediated glucose metabolism in 3T3-L1 preadipocytes. To investigate the impact on adipogenesis, 3T3-L1 preadipocytes were differentiated with each ARB in addition to standard inducers of differentiation for adipogenesis. Telmisartan dose-dependently facilitated adipogenesis and markedly augmented the mRNA expression of adipocyte fatty acid-binding protein (aP2), accompanied by an increase in the uptake of 2-deoxyglucose and protein expression of glucose transporter 4 (GLUT4). In contrast, other ARBs showed only marginal effects in these experiments. In accordance with its highest affinity of binding for PPARγ as well as the highest cell permeability, telmisartan superbly activates PPARγ among the ARBs tested, thereby providing a fresh avenue for treating hypertensive patients with metabolic derangement.

Context Primary macronodular adrenal hyperplasia (PMAH) is a rare type of Cushing or subclinical Cushing syndrome and is associated with bilateral multinodular formation. ARMC5 is one of the responsible genes for PMAH. Objectives This study was performed to identify the genotype-phenotype correlation of ARMC5 in a cohort of Japanese patients. Patients and Methods Fourteen patients with clinically diagnosed PMAH and family members of selected patients were studied for ARMC5 gene alteration and clinical phenotype. The associated nonadrenal tumor tissues were also studied. Results Of fourteen patients with PMAH, 10 had pathogenic or likely pathogenic variants of ARMC5. We found two variants. Five unrelated patients had identical variants (p.R619*). In two patients, the variant was found in offspring with the asymptomatic or presymptomatic state. Six of ten patients who tested positive for the ARMC5 pathogenic or likely pathogenic variant carried nonadrenal tumors; however, no loss of heterozygosity (LOH) or second hit of the ARMC5 gene was evident. The ARMC5 variant–positive group showed a significantly higher basal cortisol level. Furthermore, age-dependent cortisol hypersecretion was seen in the ARMC5 variant–positive group. Conclusions ARMC5 pathogenic variants are common (71%) in Japanese patients with PMAH. p.R619* might be a hot spot in Japanese patients with PMAH. Asymptomatic or presymptomatic pathogenic variant carriers were found among the family members of the patients. Although 50% of ARMC5 variant carriers had nonadrenal neoplastic lesions, no LOH or second hit of ARMC5 in the tumor tissues was evident. The ARMC5 variant–positive mutant group showed a higher basal cortisol level than the negative group.

Congenital hyperinsulinism (CHI) caused by a glucokinase- (GCK-) activating mutation shows autosomal dominant inheritance, and its severity ranges from mild to severe. A 43-year-old female with asymptomatic hypoglycemia (47 mg/dL) was diagnosed as partial adrenal insufficiency and the administration of hydrocortisone (10 mg/day) was initiated. Twelve years later, her 8-month-old grandchild was diagnosed with CHI. Heterozygosity of exon 6 c.590T>C (p.M197T) was identified in a gene analysis of GCK, which was also detected in her son and herself. The identification of GCK-activating mutations in hyperinsulinemic hypoglycemia patients may be useful for a deeper understanding of the pathophysiology involved and preventing unnecessary glucocorticoid therapy.