Pioglitazone, a thiazolidinedione, improves glycemic control primarily by increasing peripheral insulin sensitivity in patients with type 2 diabetes, whereas metformin, a biguanide, exerts its effect primarily by decreasing hepatic glucose output. In the first head-to-head, double-blind clinical trial comparing these two oral antihyperglycemic medications (OAMs), we studied the effect of 32-wk monotherapy on glycemic control and insulin sensitivity in 205 patients with recently diagnosed type 2 diabetes who were naive to OAM therapy. Subjects were randomized to either 30 mg pioglitazone or 850 mg metformin daily with titrations upward to 45 mg (77% of pioglitazone patients) and 2550 mg (73% of metformin patients), as indicated, to achieve fasting plasma glucose levels of less than 7.0 mmol/liter (126 mg/dl). Pioglitazone was comparable to metformin in improving glycemic control as measured by hemoglobin A1C and fasting plasma glucose. At endpoint, pioglitazone was significantly more effective than metformin in improving indicators of insulin sensitivity, as determined by reduction of fasting serum insulin (P = 0.003) and by analysis of homeostasis model assessment for insulin sensitivity (HOMA-S; P = 0.002). Both OAM therapies were well tolerated. Therefore, pioglitazone and metformin are equally efficacious in regard to glycemic control, but they exert significantly different effects on insulin sensitivity due to differing mechanisms of action. The more pronounced improvement in indicators of insulin sensitivity by pioglitazone, as compared with metformin monotherapy in patients recently diagnosed with type 2 diabetes who are OAM-naive, may be of interest for further clinical evaluation.

We evaluate the shared genetic regulation of mRNA molecules, proteins and metabolites derived from whole blood from 3029 human donors. We find abundant allelic heterogeneity, where multiple variants regulate a particular molecular phenotype, and pleiotropy, where a single variant associates with multiple molecular phenotypes over multiple genomic regions. The highest proportion of share genetic regulation is detected between gene expression and proteins (66.6%), with a further median shared genetic associations across 49 different tissues of 78.3% and 62.4% between plasma proteins and gene expression. We represent the genetic and molecular associations in networks including 2828 known GWAS variants, showing that GWAS variants are more often connected to gene expression in trans than other molecular phenotypes in the network. Our work provides a roadmap to understanding molecular networks and deriving the underlying mechanism of action of GWAS variants using different molecular phenotypes in an accessible tissue.

Excess liver iron content is common and is linked to the risk of hepatic and extrahepatic diseases. We aimed to identify genetic variants influencing liver iron content and use genetics to understand its link to other traits and diseases. First, we performed a genome-wide association study (GWAS) in 8,289 individuals from UK Biobank, whose liver iron level had been quantified by magnetic resonance imaging, before validating our findings in an independent cohort (n = 1,513 from IMI DIRECT). Second, we used Mendelian randomisation to test the causal effects of 25 predominantly metabolic traits on liver iron content. Third, we tested phenome-wide associations between liver iron variants and 770 traits and disease outcomes. We identified 3 independent genetic variants (rs1800562 [C282Y] and rs1799945 [H63D] in HFE and rs855791 [V736A] in TMPRSS6) associated with liver iron content that reached the GWAS significance threshold (p <5 × 10-8). The 2 HFE variants account for ∼85% of all cases of hereditary haemochromatosis. Mendelian randomisation analysis provided evidence that higher central obesity plays a causal role in increased liver iron content. Phenome-wide association analysis demonstrated shared aetiopathogenic mechanisms for elevated liver iron, high blood pressure, cirrhosis, malignancies, neuropsychiatric and rheumatological conditions, while also highlighting inverse associations with anaemias, lipidaemias and ischaemic heart disease. Our study provides genetic evidence that mechanisms underlying higher liver iron content are likely systemic rather than organ specific, that higher central obesity is causally associated with higher liver iron, and that liver iron shares common aetiology with multiple metabolic and non-metabolic diseases. Excess liver iron content is common and is associated with liver diseases and metabolic diseases including diabetes, high blood pressure, and heart disease. We identified 3 genetic variants that are linked to an increased risk of developing higher liver iron content. We show that the same genetic variants are linked to higher risk of many diseases, but they may also be associated with some health advantages. Finally, we use genetic variants associated with waist-to-hip ratio as a tool to show that central obesity is causally associated with increased liver iron content.

Tirzepatide, a once-weekly glucose-dependent insulinotropic polypeptide (GIP)/glucagon-like peptide-1 (GLP-1) receptor agonist (GIP/GLP-1 RA) improves glycemic control. Besides improvement of glycemic control, tirzepatide treatment is associated with significantly more weight loss as compared to potent selective GLP-1 receptor agonists as well as other beneficial changes in cardio-metabolic parameters, such as reduced fat mass, blood pressure, improved insulin sensitivity, lipoprotein concentrations, and circulating metabolic profile in individuals with type 2 diabetes (T2D). Some of these changes are partially associated with weight reduction. We review here the putative mechanisms of GIP receptor agonism contributing to GLP-1 receptor agonism-induced weight loss and respective findings with GIP/GLP-1 RAs, including tirzepatide in T2D preclinical models and clinical studies. Subsequently, we summarize the clinical data on weight loss and related non-glycemic metabolic changes of tirzepatide in T2D. These findings suggest that the robust weight loss and associated changes are important contributors to the clinical profile of tirzepatide for the treatment of T2D diabetes and serve as the basis for further investigations including clinical outcomes.