SummaryAging is associated with impaired fasted oxidation of nonesterified fatty acids (NEFA) suggesting a mitochondrial defect. Aging is also associated with deficiency of glutathione (GSH), an important mitochondrial antioxidant, and with insulin resistance. This study tested whether GSH deficiency in aging contributes to impaired mitochondrial NEFA oxidation and insulin resistance, and whether GSH restoration reverses these defects. Three studies were conducted: (i) in 82-week-old C57BL/6 mice, the effect of naturally occurring GSH deficiency and its restoration on mitochondrial 13 C 1 -palmitate oxidation and glucose metabolism was compared with 22-week-old C57BL/6 mice; (ii) in 20-week C57BL/6 mice, the effect of GSH depletion on mitochondrial oxidation of 13 C 1 -palmitate and glucose metabolism was studied; (iii) the effect of GSH deficiency and its restoration on fasted NEFA oxidation and insulin resistance was studied in GSHdeficient elderly humans, and compared with GSH-replete young humans. Chronic GSH deficiency in old mice and elderly humans was associated with decreased fasted mitochondrial NEFA oxidation and insulin resistance, and these defects were reversed with GSH restoration. Acute depletion of GSH in young mice resulted in lower mitochondrial NEFA oxidation, but did not alter glucose metabolism. These data suggest that GSH is a novel regulator of mitochondrial NEFA oxidation and insulin resistance in aging. Chronic GSH deficiency promotes impaired NEFA oxidation and insulin resistance, and GSH restoration reverses these defects. Supplementing diets of elderly humans with cysteine and glycine to correct GSH deficiency could provide significant metabolic benefits.

Aims/hypothesis Systemic fibroblast growth factor (FGF)21 levels and hepatic FGF21 production are increased in non-alcoholic fatty liver disease patients, suggesting FGF21 resistance. We examined the effects of exenatide on FGF21 in patients with type 2 diabetes and in a diet-induced mouse model of obesity (DIO). Methods Type 2 diabetes mellitus patients (n=24) on diet and/or metformin were randomised (using a table of random numbers) to receive additional treatment consisting of pioglitazone 45 mg/day or combined therapy with pioglitazone (45 mg/day) and exenatide (10 μg twice daily) for 12 months in an open label parallel study at the Baylor Clinic. Results Twenty-one patients completed the entire study and were included in the analysis. Pioglitazone treatment (n=10) reduced hepatic fat as assessed by magnetic resonance spectroscopy, despite a significant increase in body weight (Δ=3.7 kg); plasma FGF21 levels did not change (1.9±0.6 to 2.2±0.6 ng/ml [mean±SEM]). However, combined pioglitazone and exenatide therapy (n=11) was associated with a significant reduction of FGF21 levels (2.3±0.5 to 1.1± 0.3 ng/ml) and a greater decrease in hepatic fat. Besides weight gain observed in the pioglitazone-treated patients, lower extremity oedema was observed as a side effect in two of the ten patients. Three patients who received pioglitazone and exenatide combination therapy complained of significant nausea that was self-limiting and did not require them to leave the study. In DIO mice, exendin-4 for 4 weeks significantly reduced hepatic triacylglycerol content, decreased hepatic FGF21 protein and mRNA, and enhanced phosphorylation of hepatic AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase, although no significant difference in weight and body fat was observed. Hepatic FGF21 correlated inversely with hepatic AMPK phosphorylation Conclusions/interpretation In type 2 diabetes mellitus, combined pioglitazone and exenatide therapy is associated with a reduction in plasma FGF21 levels, as well as a greater decrease in hepatic fat than that achieved with pioglitazone therapy. In DIO mice, exendin-4 treatment reduces hepatic triacylglycerol and FGF21 protein, and enhances hepatic AMPK phosphorylation, suggesting an improvement of hepatic FGF21 resistance.

Exendin 4 (Ex4) is a glucagon-like peptide-1 receptor (GLP- 1R) agonist which is available as a short-acting injectable treatment for type 2 diabetes. Our aim was to characterize the long-term effects of elevated steady-state levels of Ex4 provided by in vivo gene therapy. We constructed a helper-dependent adenoviral (HDAd) vector for long-term expression of Ex4 in vivo. A high-fat diet (HFD)-induced obesity (DIO) mouse model was chosen to approximate the metabolic derangements seen in obese patients. Mice were treated with a single injection of HDAd-Ex4 and were monitored for 15 weeks. Both hepatic Ex4 RNA and plasma Ex4 were detectable at the end of the study. HDAd-Ex4 treatment improved glucose homeostasis without increasing insulin levels. However, there was evidence of enhanced insulin action and decreased gluconeogenic enzyme expression. HDAd-Ex4 caused decreased weight gain without detectable changes in food intake, in part, due to increases in energy expenditure (EE). HDAd-Ex4 DIO mice also had reduced hepatic fat and an improved adipokine profile. In the liver, there was decreased expression of genes that were involved in de novo fatty acid synthesis. These observations are important in considering the development of longer acting GLP-1R agonists for the treatment of type 2 diabetes.

GRADE (Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study) is a 36-center unmasked, parallel treatment group, randomized controlled trial evaluating four diabetes medications added to metformin in people with type 2 diabetes (T2DM). We report baseline characteristics and compare GRADE participants to a National Health and Nutrition Examination Survey (NHANES) cohort. RESEARCH DESIGN AND METHODS Participants were age ‡30 years at the time of diagnosis, with duration of T2DM <10 years, HbA 1c 6.8-8.5% (51-69 mmol/mol), prescribed metformin monotherapy, and randomized to glimepiride, sitagliptin, liraglutide, or insulin glargine. RESULTS At baseline, GRADE's 5,047 randomized participants were 57.2 6 10.0 years of age, 63.6% male, with racial/ethnic breakdown of 65.7% white, 19.8% African American, 3.6% Asian, 2.7% Native American, 7.6% other or unknown, and 18.4% Hispanic/ Latino. Duration of diabetes was 4.2 6 2.8 years, with mean HbA 1c of 7.5 6 0.5% (58 6 5.3 mmol/mol), BMI of 34.3 6 6.8 kg/m 2 , and metformin dose of 1,944 6 204 mg/day. Among the cohort, 67% reported a history of hypertension, 72% a history of hyperlipidemia, and 6.5% a history of heart attack or stroke. Applying GRADE inclusion criteria to NHANES indicates enrollment of a representative cohort with T2DM on metformin monotherapy (NHANES cohort average age, 57.9 years; mean HbA 1c , 7.4% [57 mmol/mol]; BMI, 33.2 kg/m 2 ; duration, 4.2 6 2.5 years; and 7.2% with a history of cardiovascular disease). CONCLUSIONS The GRADE cohort represents patients with T2DM treated with metformin requiring a second diabetes medication. GRADE will inform decisions about the clinical effectiveness of the addition of four classes of diabetes medications to metformin. The optimal medication management of hyperglycemia in type 2 diabetes (T2DM) is not established. In addition to lifestyle intervention, metformin is the recommended initial medication in T2DM due to its glycemic effectiveness, lack of associated hypoglycemia or weight gain, low cost, and evidence of long-term benefit and safety

Objective Unprovoked “A-β+” Ketosis-Prone Diabetes (KPD), a unique diabetic syndrome of adult-onset, obesity and proneness to ketoacidosis, is associated with rapid recovery of β cell function and insulin-independence. Whereas most patients experience prolonged remission, a subset relapses early to insulin dependence. We sought to define factors associated with early relapse. Methods We utilized a prospective, longitudinal database to analyze 50 unprovoked A-β+ KPD patients with ≥2 measurements of β cell function and glycemia following baseline assessment. Results 19 patients (38%) relapsed to insulin dependence <1y after the index DKA episode, while 31 (62%) remained insulin-independent for >1y (median 4.2y). Younger age at baseline (OR=0.947, P=0.033), and lower HOMA2-%β (OR=0.982, P=0.001), lower HOMA2-IR (OR=0.582, P=0.046) and higher HbA1c at 1y (OR=1.71, P=0.002) were associated with early relapse. A multivariate model with these variables and the interaction of HOMA2-%β and HbA1c at 1y provided a good fit (P<0.05). Conclusions Relapse to insulin dependence in unprovoked A-β+ KPD patients is associated with younger age and, after 1y, lack of robust increase in β cell functional reserve, and suboptimal glycemic control. Measurements of these parameters 1y after the index DKA episode can be used to assess the need for insulin therapy.