Jin P

Overexpression of Insig-1 protects β cell against glucolipotoxicity via SREBP-1c

BackgroundHigh glucose induced lipid synthesis leads to β cell glucolipotoxicity. Sterol regulatory element binding protein-1c (SREBP-1c) is reported to be partially involved in this process. Insulin induced gene-1 (Insig-1) is an important upstream regulator of Insig-1-SREBPs cleavage activating protein (SCAP)-SREBP-1c pathway. Insig-1 effectively blocks the transcription of SREBP-1c, preventing the activation of the genes for lipid biosynthesis. In this study, we aimed to investigate whether Insig-1 protects β cells against glucolipotoxicity.MethodsAn Insig-1 stable cell line was generated by overexpression of Insig-1 in INS-1 cells. The expression of Insig-1 was evaluated by RT-PCR and Western blotting, then, cells were then treated with standard (11.2 mM) or high (25.0 mM) glucose for 0 h, 24 h and 72 h. Cell viability, apoptosis, glucose stimulated insulin secretion (GSIS), lipid metabolism and mRNA expression of insulin secretion relevant genes such as IRS-2, PDX-1, GLUT-2, Insulin and UCP-2 were evaluated.ResultsWe found that Insig-1 suppressed the high glucose induced SREBP-1c mRNA and protein expression. Our results also showed that Insig-1 overexpression protected β cells from ER stress-induced apoptosis by regulating the proteins expressed in the IRE1α pathway, such as p-IRE1α, p-JNK, CHOP and BCL-2. In addition, Insig-1 up-regulated the expression of IRS-2, PDX-1, GLUT-2 and Insulin, down-regulated the expression of UCP-2 and improved glucose stimulated insulin secretion (GSIS). Finally, we found that Insig-1 inhibited the lipid accumulation and free fatty acid (FFA) synthesis in a time-dependent manner.ConclusionsThere results suggest that Insig-1 may play a critical role in protecting β cells against glucolipotoxicity by regulating the expression of SREBP-1c.

Identification of a novel LEMD3 Y871X mutation in a three-generation family with osteopoikilosis and review of the literature

AbstractIntroductionOsteopoikilosis is a rare and benign autosomal dominant genetic disorder, characterized by a symmetric but unequal distribution of multiple hyperostotic areas in different parts of the skeleton. Recent studies have reported loss-of-function mutations in the LEM domain containing 3 (LEMD3) gene, encoding an inner nuclear membrane protein, as a cause of osteopoikilosis.MethodsWe investigated LEMD3 gene in a three-generation family from China, with six patients affected with osteopoikilosis. Peripheral blood samples were collected from family members and 100 healthy controls. All exons of the LEMD3 gene and adjacent exon–intron sequences were amplified by PCR and subsequently sequenced.ResultsA novel heterozygous c.2612_2613insA (p.Y871X) mutation in exon 13 of LEMD3 was identified, which resulted in a frame shift predicted to generate a premature stop codon at amino acid position 871. The mutation co-segregates with the osteopoikilosis phenotype and was not found in 100 ethnically matched controls. ConclusionWe identified a new mutation in LEMD3 gene, accounting for the familial case of osteopoikilosis. In addition we also review the clinical manifestation, diagnosis and treatment of osteopoikilosis.

Extensive ARMC5 genetic variance in primary bilateral macronodular adrenal hyperplasia that started with exophthalmos: a case report

BackgroundPrimary bilateral macronodular adrenal hyperplasia is a rare cause of Cushing’s syndrome characterized by the presence of bilateral secretory adrenal nodules. Recent studies have shown that primary bilateral macronodular adrenal hyperplasia is caused by combined germline and somatic mutations of the ARMC5 gene. Exophthalmos is an underappreciated sign of Cushing’s syndrome.Case presentationA 52-year-old Chinese woman with progressively worsening bilateral proptosis presented to our hospital. Subsequently she was diagnosed as having primary bilateral macronodular adrenal hyperplasia and underwent bilateral laparoscopic adrenalectomy. Genomic deoxyribonucleic acid was isolated from lymphocytes as well as seven different adrenal nodules and the ARMC5 sequence was determined by Sanger sequencing. We identified one heterozygous ARMC5 germline mutation c.682C>T (p. Gln228*) and five heterozygous somatic mutations (c.310delG, c.347_357del11, c.267delC, c.283_289del7, and c.205-322del118) in five different adrenal nodules. All mutations are novel and were not found in any of the available online databases. To test whether the ARMC5 mutation induced messenger ribonucleic acid decay, real-time reverse transcriptase polymerase chain reaction was performed on patient and control adrenal tissue. We found that the adrenal cortex of our patient showed a low ARMC5 messenger ribonucleic acid expression compared with normal adrenal cortex, possibly as a result of nonsense-mediated messenger ribonucleic acid decayConclusionsWe demonstrated extensive genetic diversity of ARMC5 in a patient with primary bilateral macronodular adrenal hyperplasia that started with exophthalmos, which contributes to further understanding of the pathogenesis of this disease. Early recognition of atypical symptoms and screening for ARMC5 mutation in patients with primary bilateral macronodular adrenal hyperplasia has important clinical implications for the diagnosis and genetic counseling.

Association of medullary sponge kidney and hyperparathyroidism with RET G691S/S904S polymorphism: a case report

BackgroundMedullary sponge kidney is a rare renal malformation, which usually manifests as nephrocalcinosis, renal tubular acidosis, and recurrent urinary tract infections. Medullary sponge kidney is often associated with renal developmental anomalies and tumors, and its exact pathogenesis is not yet clearly explained. Given the key role of the interaction of glial cell line-derived neurotrophic factor gene, GDNF, and the “rearranged during transfection” proto-oncogene, RET, in kidney and urinary tract development, variations in these genes are proposed to be candidates for medullary sponge kidney. Hyperparathyroidism is observed in a few patients with medullary sponge kidney, but the exact pathogenesis of this association is unknown. This case report highlights the coexistence of these two conditions associated with RET polymorphism, which contributes toward the understanding of the pathogenesis of medullary sponge kidney.Case presentationA 52-year-old Chinese woman with recurrent renal stones presented to our hospital. Subsequently she was diagnosed as having medullary sponge kidney and tertiary hyperparathyroidism and underwent parathyroidectomy. Genomic DNA was isolated from lymphocytes and the GDNF and RET genes were determined by Sanger sequencing. Two RET polymorphisms were found in our patient, one was nonsynonymous c.2071G>A (G691S; rs1799939) located in exon 11, the other was synonymous c.2712C>G. (p.S904S; rs1800863) located in exon 15.ConclusionsWe demonstrated a case of medullary sponge kidney combined with tertiary hyperparathyroidism, which contributes to further understanding of the pathogenesis of this disease. Besides, we also found RET G691S/S904S polymorphism in this patient, but additional studies are required to explore the role of the RET gene in medullary sponge kidney with hyperparathyroidism.

Identification of a novel GNAS mutation in a case of pseudohypoparathyroidism type 1A with normocalcemia

BackgroundPseudohypoparathyroidism type 1A (PHP1A) is a rare genetic disease primarily characterized by resistance to parathyroid hormone along with hormonal resistance and other features of Albright hereditary osteodystrophy (AHO). It is caused by heterozygous inactivating mutations in the maternal allele of the GNAS gene, which encodes the stimulatory G-protein alpha subunit (Gsα) and regulates production of the second messenger cyclic AMP (cAMP). Herein, we report a case of of PHP1A with atypical clinical manifestations (oligomenorrhea, subclinical hypothyroidism, and normocalcemia) and explore the underlying genetic cause in this patient.MethodsBlood samples were collected from the patient, her family members, and 100 healthy controls. The 13 exons and flanking splice sites of the GNAS gene were amplified by PCR and sequenced. To further assess whether the novel mutation resulted in gain or loss of function of Gsα, we examined the level of cAMP activity associated with this mutation through in vitro functional studies by introducing the target mutation into a human GNAS plasmid.ResultsA novel heterozygous c.715A > G (p.N239D) mutation in exon 9 of the GNAS gene was identified in the patient. This mutation was also found in her mother, who was diagnosed with pseudopseudohypoparathyroidism. An in vitro cAMP assay showed a significant decrease in PTH-induced cAMP production in cells transfected with the mutant plasmid, compared to that in the wild-type control cells (P < 0.01), which was consistent with loss of Gsa activity.ConclusionWe identified a novel GNAS mutation that altered Gsα function, which furthers our understanding of the pathogenesis of this disease. Screening for GNAS mutations should be considered in suspected cases of PHP1A even if the classical signs are not present.