Cardiac steatosis in diabetes mellitus: a 1H-magnetic resonance spectroscopy study.

BACKGROUND: The risk of heart failure in type 2 diabetes mellitus is greater than can be accounted for by hypertension and coronary artery disease. Rodent studies indicate that in obesity and type 2 diabetes mellitus, lipid overstorage in cardiac myocytes produces lipotoxic intermediates that cause apoptosis, which leads to heart failure. In humans with diabetes mellitus, cardiac steatosis previously has been demonstrated in explanted hearts of patients with end-stage nonischemic cardiomyopathy. Whether cardiac steatosis precedes the onset of cardiomyopathy in individuals with impaired glucose tolerance or in patients with type 2 diabetes mellitus is unknown. METHODS AND RESULTS: To represent the progressive stages in the natural history of type 2 diabetes mellitus, we stratified 134 individuals (age 45+/-12 years) into 1 of 4 groups: (1) lean normoglycemic (lean), (2) overweight and obese normoglycemic (obese), (3) impaired glucose tolerance, and (4) type 2 diabetes mellitus. Localized (1)H magnetic resonance spectroscopy and cardiac magnetic resonance imaging were used to quantify myocardial triglyceride content and left ventricular function, respectively. Compared with lean subjects, myocardial triglyceride content was 2.3-fold higher in those with impaired glucose tolerance and 2.1-fold higher in those with type 2 diabetes mellitus (P<0.05). Left ventricular ejection fraction was normal and comparable across all groups. CONCLUSIONS: In humans, impaired glucose tolerance is accompanied by cardiac steatosis, which precedes the onset of type 2 diabetes mellitus and left ventricular systolic dysfunction. Thus, lipid overstorage in human cardiac myocytes is an early manifestation in the pathogenesis of type 2 diabetes mellitus and is evident in the absence of heart failure.

Effect of pioglitazone therapy on myocardial and hepatic steatosis in insulin-treated patients with type 2 diabetes.

High levels of myocardial and hepatic triglyceride are common in obesity and type 2 diabetes. Monotherapy with thiazolidinedione agents reduces hepatic steatosis by up to 50% in patients with type 2 diabetes. It is not known if treatment with a thiazolidinedione added to insulin has a similar beneficial antisteatotic effect. The aim of our study was to determine whether the addition of pioglitazone to insulin treatment in patients with type 2 diabetes has antisteatotic action in the heart and the liver. Thirty-two patients were randomized to 6 months of treatment with insulin or insulin plus pioglitazone. In addition to blood tests, we evaluated myocardial and hepatic triglyceride content, as well as subcutaneous and visceral fat mass at the L2 level, by magnetic resonance spectroscopy and imaging, respectively. Despite weight and subcutaneous fat mass gain, hemoglobin A1c was significantly reduced by both treatments. Myocardial and hepatic triglyceride contents were reduced by the treatment with pioglitazone plus insulin (p = .02 and .03, respectively) but not by the treatment with insulin. Systolic and diastolic blood pressure and heart function remained unchanged in both groups. The addition of pioglitazone to insulin therapy reduced myocardial and hepatic steatosis, consistent with the reported ability of the thiazolidinedione agents to redistribute fat from nonadipose to subcutaneous adipose depots.

Therapeutic options for the prevention of type 2 diabetes mellitus in the metabolic syndrome.

The increasing prevalence of metabolic syndrome has created an impetus to prevent complications such as diabetes. There are no defined treatments for metabolic syndrome apart from addressing each of its components such as obesity, hypertension, dyslipidemia, and hyperglycemia. To evaluate diabetes-prevention strategies, we performed a Medline search and identified evidence suggesting that lifestyle intervention and certain medications can prevent diabetes. In addition, there are several agents on the horizon that seem promising. The mechanism responsible for diabetes prevention relates to improved insulin resistance as a result of weight loss or other processes. Lifestyle interventions and medications such as metformin are effective and safe in long-term prevention studies. However, the safety and efficacy of newer agents need clarification.

Novel insulin analogues and its mitogenic potential.

Insulin analogues were developed to modify the structure of the human insulin molecule in order to more accurately approximate the endogenous secretion of insulin. With the help of recombinant technology and site-directed mutagenesis, the insulin molecule can be modified to either delay or shorten absorption time, providing better insulin treatment options and facilitating the achievement of glycaemic goals. Changing the structure of the insulin molecule, however, may significantly alter both its metabolic and mitogenic activity. Multiple factors such as residence time on the receptor, dissociation rate, rate of receptor internalization and the degree of phosphorylation of signalling proteins can affect the mitogenic potencies of insulin analogues. Changes in the structure of the insulin have raised concern about the safety of the insulin analogues. For example, questions have emerged about the relationship between the use of insulin lispro and insulin glargine and the progression of diabetic retinopathy. Two studies have shown progression of retinopathy with the use of insulin lispro. However, others have not confirmed these results, and causality could not be proven as progression of retinopathy can occur with rapid improvement in glycaemic control, and methods of assessments among studies were not consistent. Therefore, we examine the metabolic and mitogenic characteristics of the three insulin analogues, insulin lispro, insulin aspart and insulin glargine, that are currently on the market, as well as the two insulin analogues, insulin glulisine and insulin detemir, that are soon going to be available for clinical use.