Hyperproinsulinemia in obesity and in type 2 diabetes and its relation to cardiovascular disease

Metformin restores prohormone processing enzymes and normalizes aberrations in secretion of proinsulin and insulin in palmitate-exposed human islets

AIM

To elucidate how proinsulin synthesis and insulin was affected by metformin under conditions of nutrient overstimulation.

MATERIALS AND METHODS

Isolated human pancreatic islets from seven donors were cultured at 5.5 mmol/L glucose and 0.5 mmol/L palmitate for 12, 24 or 72 h. Metformin (25 μmol/L) was introduced after initial 12 h with palmitate. Proinsulin and insulin were measured. Expression of prohormone convertase 1/3 (PC1/3) and carboxypeptidase E (CPE), was determined by western blot. Adolescents with obesity, treated with metformin and with normal glucose tolerance (n = 5), prediabetes (n = 14), or type 2 diabetes (T2DM; n = 7) were included. Fasting proinsulin, insulin, glucose, 2-h glucose and glycated haemoglobin were measured. Proinsulin/insulin ratio (PI/I) was calculated.

RESULTS

In human islets, palmitate treatment for 12 and 24 h increased proinsulin and insulin proportionally. After 72 h, proinsulin but not insulin continued to increase which was coupled with reduced expression of PC1/3 and CPE. Metformin normalized expression of PC1/3 and CPE, and proinsulin and insulin secretion. In adolescents with obesity, before treatment, fasting proinsulin and insulin concentrations were higher in subjects with T2DM than with normal glucose tolerance. PI/I was reduced after metformin treatment in subjects with T2DM as well as in subjects with prediabetes, coupled with reduced 2-h glucose and glycated haemoglobin.

CONCLUSIONS

Metformin normalized proinsulin and insulin secretion after prolonged nutrient-overstimulation, coupled with normalization of the converting enzymes, in isolated islets. In adolescents with obesity, metformin treatment was associated with improved PI/I, which was coupled with improved glycaemic control.

Cord Blood IGF-I, Proinsulin, Leptin, HMW Adiponectin, and Ghrelin in Short or Skinny Small-for-Gestational-Age Infants

CONTEXT

Small-for-gestational-age (SGA) is an indicator of poor fetal growth "programming" an elevated risk of type 2 diabetes in adulthood. Little is known about early-life endocrine characteristics in SGA subtypes. Stunting (short) and wasting (skinny) are considered distinct SGA phenotypes in neonatal prognosis.

OBJECTIVES

This work aimed to assess whether SGA infants with stunting or wasting have similar alterations in neonatal endocrine metabolic health biomarkers.

METHODS

This was a nested case-control study based on the 3D (Design, Develop, and Discover) birth cohort in Canada. The study subjects were 146 SGA (birth weight < 10th percentile) and 155 optimal-for-gestational age (OGA, 25th-75th percentiles) infants. Stunting was defined as birth length less than the 10th percentile, and wasting as body mass index less than the 10th percentile for sex and gestational age, respectively. Main outcome measures included cord plasma concentrations of insulin-like growth factor I (IGF-I), proinsulin, leptin, high-molecular-weight (HMW) adiponectin, and ghrelin.

RESULTS

Comparing to OGA infants adjusted for maternal and neonatal characteristics, SGA infants with either stunting only or wasting only had lower cord plasma IGF-I and leptin concentrations. HMW adiponectin concentrations were lower in SGA infants with wasting only (P = .004), but similar in SGA infants with stunting only (P = .816). Only SGA infants with both stunting and wasting had substantially lower proinsulin (P < .001) and higher ghrelin concentrations (P < .001) than OGA infants.

CONCLUSION

This study is the first to demonstrate that SGA infants with wasting only are characterized by low HMW adiponectin concentrations, whereas those with stunting only are not. SGA with both stunting and wasting are characterized by low proinsulin and high ghrelin concentrations.

In silico analysis of non-synonymous missense SNPs (nsSNPs) in CPE, GNAS genes and experimental validation in type II diabetes mellitus through Next Generation Sequencing

Non-synonymous missense SNPs (nsSNPs) in CPE and GNAS genes were investigated computationally. In silico identified nsSNPs were experimentally validated in type II diabetes mellitus (T2DM) in Pakistani Pathan population using next generation sequencing (NGS). Sixty two high-risk nsSNPs in CPE and 44 in GNAS were identified. Only 12 in GNAS were clinically significant. Thirty six high-risk nsSNPs in CPE and 08 clinically significant nsSNPs in GNAS lies in the most conserved regions. I-mutant predicted that nsSNPs decrease the proteins stability and ModPred predicted 20 and 12 post-translational modification sites in CPE and GNAS proteins respectively. Ramachandran plot showed 88.7% residues are in the most favored region of protein models. By experimentation, none of the nsSNPs were found to be associated with T2DM. In conclusion, this study differentiates the deleterious nsSNPs from the neutral ones. Although nsSNPs are not associated with T2DM, they can be targeted in other CPE and GNAS genes related disorders.