Acetylsalicylic acid protects erectile function in diabetic rats

We aimed to evaluate the effect of acetylsalicylic acid (ASA) treatment on diabetes-induced erectile dysfunction. Adult male Sprague-Dawley rats were divided into four groups as follows: (i) control (C), (ii) diabetic (D), (iii) ASA-treated control (C+ASA) and (iv) ASA-treated diabetic (D+ASA) groups. In groups 2 and 4, diabetes was induced by injection of 35 mg kg(-1) streptozotocin. ASA (100 mg kg(-1) day(-1) , orally) was administrated to rats in groups 3 and 4 for 8 weeks. Both intracavernosal pressure (ICP) and mean arterial blood pressure (MAP) were measured in in vivo studies. In organ bath, the relaxation responses to acetylcholine (ACh), electrical field stimulation (EFS) and sodium nitroprusside were tested in corpus cavernosum (CC) strips. The mRNA expression for neuronal nitric oxide synthase (nNOS) was calculated using reverse transcription polymerase chain reaction technique. In in vivo experiments, diabetic rats displayed reduced ICP/MAP values, which were normalised with ASA treatment. The relaxant response to high-dose ACh and EFS at low frequencies (1-8 Hz) in CC strips from the D+ASA group were significantly higher when compared to the D group. Treatment with ASA normalised the raised mRNA expressions of nNOS in diabetic penile tissues. ASA may be involved in mRNA of protein synthesis of NO released from nonadrenergic and noncholinergic cavernosal nerve in diabetes.

The changes in beta-adrenoceptor-mediated cardiac function in experimental hypothyroidism: the possible contribution of cardiac beta3-adrenoceptors

Thyroid hormone deficiency has been reported to decrease expression and function of both beta(1)- and beta(2)-adrenoceptor in different tissues including heart. The purpose of this study was to examine the possible contribution of beta(3)-adrenoceptors to cardiac dysfunction in hypothyroidism. In addition, effect of this pathology on beta(1)- and beta(2)-adrenoceptor was investigated. Hypothyroidism was induced by adding methimazole (300 mg/l) to drinking water of rats for 8 weeks. Cardiac hemodynamic parameters were measured in anesthetised rats in vivo. Responses to beta-adrenoceptor agonists were examined in rat papillary muscle in vitro. We also studied the effect of hypotyroidism on mRNA expression of beta-adrenoceptors, Gialpha, GRK, and eNOS in rat heart. All of the hemodynamic parameters (systolic, diastolic and mean arterial pressure, left ventricular pressure, heart rate, +dp/dt, and -dp/dt) were significantly reduced by the methimazole treatment. The negative inotropic effect elicited by BRL 37344 (a beta(3)-adrenoceptor preferential agonist) and positive inotropic effects produced by isoprenaline and noradrenaline, respectively, were significantly decreased in papillary muscle of hypothyroid rats as compared to those of controls. On the other hand, hypothyroidism resulted in increased cardiac beta(2)- and beta(3)-adrenoceptor, Gialpha(2), Gialpha(3), GRK3, and eNOS mRNA expressions. However, beta(1)-adrenoceptor and GRK2 mRNA expressions were not changed significantly in this pathology. These results show that mRNA expression of beta(3)-adrenoceptors as well as the signalling pathway components mediated through beta(3)-adrenoceptors are significantly increased in hypothyroid rat heart. Since we could not correlate these alternates with the decreased negative inotropic response mediated by this receptor subtype, it is not clear whether these changes are important for hypothyroid induced reduction in cardiac function.

Lipoatrophy revisited

The lipoatrophy syndromes are a heterogeneous group of syndromes characterized by a paucity of adipose tissue. Severe lipoatrophy is associated with insulin-resistant diabetes mellitus (DM). The loss of adipose tissue can have a genetic, immune, or infectious/drug-associated etiology. Causative mutations have been identified in patients for one form of partial lipoatrophy--Dunnigan-type familial partial lipodystrophy. Experiments using lipoatrophic mice demonstrate that the diabetes results from the lack of fat and that leptin deficiency is a contributing factor. Thiazolidinedione therapy improves metabolic control in lipoatrophic patients; the efficacy of leptin treatment is currently being investigated.

Adipose tissue is required for the antidiabetic, but not for the hypolipidemic, effect of thiazolidinediones

There is uncertainty about the site(s) of action of the antidiabetic thiazolidinediones (TZDs). These drugs are agonist ligands of the transcription factor PPAR gamma, which is abundant in adipose tissue but is normally present at very low levels in liver and muscle. We have studied the effects of TZDs in A-ZIP/F-1 mice, which lack white adipose tissue. The A-ZIP/F-1 phenotype strikingly resembles that of humans with severe lipoatrophic diabetes, including the lack of fat, marked insulin resistance and hyperglycemia, hyperlipidemia, and fatty liver. Rosiglitazone or troglitazone treatment did not reduce glucose or insulin levels, suggesting that white adipose tissue is required for the antidiabetic effects of TZDs. However, TZD treatment was effective in lowering circulating triglycerides and increasing whole body fatty acid oxidation in the A-ZIP/F-1 mice, indicating that this effect occurs via targets other than white adipose tissue. A-ZIP/F-1 mice have markedly increased liver PPAR gamma mRNA levels, which may be a general property of fatty livers. Rosiglitazone treatment increased the triglyceride content of the steatotic livers of A-ZIP/F-1 and ob/ob mice, but not the "lean" livers of fat-transplanted A-ZIP/F-1 mice. In light of this evidence that rosiglitazone acts differently in steatotic livers, the effects of rosiglitazone, particularly on hepatic triglyceride levels, should be examined in humans with hepatic steatosis.

Efficacy and safety of troglitazone in the treatment of lipodystrophy syndromes

BACKGROUND

Troglitazone promotes adipocyte differentiation in vitro and increases insulin sensitivity in vivo. Therefore, troglitazone may have therapeutic benefit in lipoatrophic diabetes.

OBJECTIVE

To determine whether troglitazone ameliorates hyperglycemia and hypertriglyceridemia or increases fat mass in lipoatrophic patients.

DESIGN

Open-labeled prospective study.

SETTING

United States and Canada.

PATIENTS

20 patients with various syndromes associated with lipoatrophy or lipodystrophy.

INTERVENTION

6 months of therapy with troglitazone, 200 to 600 mg/d.

MEASUREMENTS

Levels of hemoglobin A1c triglycerides, free fatty acids, and insulin; respiratory quotient; percentage of body fat; liver volume; and regional fat mass.

RESULTS

In the 13 patients with diabetes who completed 6 months of troglitazone therapy, hemoglobin A1c levels decreased by a mean of 2.8% (95% CI, 1.9% to 3.7%; P < 0.001). In all 19 study patients, fasting triglyceride levels decreased by 2.6 mmol/L (230 mg/dL) (CI, 0.7 to 4.5 mmol/L [62 to 398 mg/dL]; P = 0.019) and free fatty acid levels decreased by 325 micromol/L (CI, 135 to 515 micromol/L; P = 0.035). The respiratory quotient decreased by a mean of 0.12 (CI, 0.08 to 0.16; P < 0.001), suggesting that troglitazone promoted oxidation of fat. Body fat increased by a mean of 2.4 percentage points (CI, 1.3 to 4.5 percentage points; P = 0.044). Magnetic resonance imaging showed an increase in subcutaneous adipose tissue but not in visceral fat. In one patient, the serum alanine aminotransferase level increased eightfold during the 10th months of troglitazone treatment but normalized 3 months after discontinuation of treatment Liver biopsy revealed an eosinophilic infiltrate, suggesting hypersensitivity reaction as a cause of hepatotoxicity.

CONCLUSION

Troglitazone therapy improved metabolic control and increased body fat in patients with lipoatrophic diabetes. The substantial benefits of troglitazone must be balanced against the risk for hepatotoxicity, which can occur relatively late in the treatment course.

A gene for congenital generalized lipodystrophy maps to human chromosome 9q34

Congenital generalized lipodystrophy (CGL, Berardinelli-Seip Syndrome, OMIM # 269700) is a rare autosomal recessive disorder characterized by near complete absence of adipose tissue from birth. Affected individuals have marked insulin resistance, hypertriglyceridemia and acanthosis nigricans, and develop diabetes mellitus during teenage years. The genetic defect for CGL is unknown. A semi-automated genome-wide scan with a set of highly polymorphic short tandem repeats (STR) was carried out in 17 well-characterized pedigrees and identified a locus for CGL to chromosome 9q34. The maximum two-point lod score obtained was 3.6 at D9S1818 (theta(max) = 0.05). There was evidence for genetic heterogeneity (alpha = 0.73) and 2 of the pedigrees were unlinked. Multipoint linkage analysis excluding the 2 unlinked families yielded a peak lod score of 5.4 between loci D9S1818 and D9S1826. The CGL1 critical region harbors a plausible candidate gene encoding the retinoid X receptor alpha (RXRA) that plays a central role in adipocyte differentiation. Identification of the CGL gene(s) will contribute to our understanding of the adipocyte differentiation and elucidation of the mechanisms of insulin resistance in disorders of adipose tissue.