Role of Oxidative Stress and Mitochondrial Dysfunction in Skeletal Muscle in Type 2 Diabetic Patients

Type 2 diabetes can increase the risk of skeletal muscle dysfunction and, consequently, that of cardiovascular diseases, including coronary artery disease and stroke. It is also related to a reduced capacity for exercise, but the underlying mechanism is only partially understood. There are several factors that contribute to the development of skeletal muscle dysfunction, of which oxidative stress and mitochondrial dysfunction are among the most important. This review discusses the role of oxidative stress in the development and progression of skeletal and cardiac dysfunction associated with diabetes. It also provides an overview of the potential actions of antioxidants in general and mitochondria-targeted antioxidants in particular in the treatment of muscle dysfunction in type 2 diabetes.

Influence of obesity on atherogenic dyslipidemia in women with polycystic ovary syndrome

BACKGROUND

Obesity is known to underlie, at least partially, dyslipidemia in polycystic ovary syndrome (PCOS), but it is unclear whether PCOS status per se increases the risk of alterations of lipoprotein subfractions, which differ in size and atherogenic potential. Our objective was to evaluate whether PCOS influences lipoprotein profile and LDL and HDL subfractions and to study the impact of obesity on these parameters.

MATERIALS AND METHODS

This was a case-control study conducted in an academic medical centre. The study population consisted of 54 women of fertile age with PCOS and 60 controls adjusted for age and BMI. Biochemical lipid profile and LDL and HDL lipoprotein subfractions (measured using Lipoprint System).

RESULTS

Lean PCOS women exhibited lower HDL cholesterol and apolipoprotein AI levels than controls, although these differences were not associated with alterations of lipoprotein subfractions. All obese subjects, whether PCOS or controls, displayed lipid parameters typical of atherogenic dyslipidemia, although the former group had lower levels of large HDL, higher levels of small HDL subfractions and a higher percentage of VLDL than the latter. These differences were associated with a greater prevalence of non-A LDL pattern (25.0%) in obese PCOS subjects than in obese controls (4.3%).

CONCLUSIONS

PCOS does not constitute an additional risk factor for cardiovascular disease in lean women, but leads to a lipid profile characteristic of atherogenic dyslipidemia and an altered pattern of lipoprotein subfraction when associated with obesity.

Relation between lipoprotein subfractions and TSH levels in the cardiovascular risk among women with subclinical hypothyroidism

OBJECTIVE

Subclinical hypothyroidism (SCH) is a common condition associated with increased cardiovascular risk. A standard treatment is yet to be established, as there is no consensus on the TSH cut-off values which should be used as indicators. Thus, the aim of this study was to assess cardiovascular risk in patients with SCH and to differentiate it according to TSH levels.

DESIGN

This was an observational study conducted in an academic medical centre.

PATIENTS

The study population consisted of 95 middle-aged women recently diagnosed with SCH and 65 euthyroid controls.

MEASUREMENTS

We measured anthropometric parameters, lipid cardiovascular risk markers and lipoprotein subclasses of HDL and LDL.

RESULTS

Patients with SCH exhibited a significant increase in triglycerides and atherogenic index of plasma and a significant reduction in HDL-cholesterol with respect to the control group after adjusted by age and BMI. A similar lipid profile was observed in both SCH groups. However, patients with TSH levels higher than 10 mIU/l showed a significant reduction in LDL particle size, which was associated with a higher prevalence of atherogenic pattern B.

CONCLUSIONS

Our findings indicate that cardiovascular risk is affected in patients with TSH levels over 10 mIU/l, who have a lipid profile characteristic of atherogenic dyslipidemia.

The effects of aging on dopaminergic neurotransmission: a microPET study of [11C]-raclopride binding in the aged rodent brain

Rodent models are frequently used in aging research to investigate biochemical age effects and aid in the development of therapies for pathological and non-pathological age-related degenerative processes. In order to validate the use of animal models in aging research and pave the way for longitudinal intervention-based animal studies, the consistency of cerebral aging processes across species needs to be evaluated. The dopaminergic system seems particularly susceptible to the aging process, and one of the most consistent findings in human brain aging research is a decline in striatal D2-like receptor (D2R) availability, quantifiable by positron emission tomography (PET) imaging. In this study, we aimed to assess whether similar age effects can be discerned in rat brains, using in vivo molecular imaging with the radioactive compound [(11)C]-raclopride. We observed a robust decline in striatal [(11)C]-raclopride uptake in the aged rats in comparison to the young control group, comprising a 41% decrement in striatal binding potential. In accordance with human studies, these results indicate that substantial reductions in D2R availability can be measured in the aged striatal complex. Our findings suggest that rat and human brains exhibit similar biochemical alterations with age in the striatal dopaminergic system, providing support for the pertinence of rodent models in aging research.

Comparative study of several lymphocyte functions in two strains of mice with different models of endotoxic shock

Previously, the changes in phagocyte functions such as adherence, chemotaxis or TNFalpha production were found to be associated with oxidative stress in endotoxin-induced septic shock. However, in this type of oxidative stress the lymphocyte involvement has rarely been studied. In the present report, we analyzed the above functions in peritoneal lymphocytes from male and female BALB/c mice with a lethal endotoxic shock caused by intraperitoneal injection of E. coli lipopolysaccharide (LPS) (100 mg/kg), male and female Swiss mice with lethal endotoxic shock caused by intraperitoneal injection of LPS (150 and 250 mg/kg, respectively) or non-lethal endotoxic shock (100 mg/kg). In peritoneal lymphocytes obtained at 0, 2, 4, 12 or 24 h after LPS injection, the first two functions of these cells in the immune response, i.e. adherence to tissues and directed migration (chemotaxis), were studied. At 0, 0.5, 1, 1.5, 2, 4, 12 and 24 h after LPS injection, TNFalpha released by lymphocytes was also analyzed. The results show that endotoxic shock increases the adherence and TNFalpha release, and decreases the chemotaxis of peritoneal lymphocytes. These changes were more significant in mice with lethal than with non-lethal endotoxic shock, a fact that confirms the important role of lymphocytes during endotoxic shock.

Several functions of immune cells in mice changed by oxidative stress caused by endotoxin

We have studied natural killer (NK) activity, lymphoproliferative response, the release of several cytokines (IL-2, TNF alpha and IL-1 beta) and the ROS production in peritoneal leukocytes obtained 0, 2, 4, 12 and 24 h after lipopolysaccharide (LPS) injection. Lethal septic shock (100 % mortality occurred at 30 h after LPS administration) was caused in female BALB/c mice by intraperitoneal injection of 100 mg/kg of E. coli LPS. Cytotoxicity and lymphoproliferation assay were preformed together with the measurement of IL-1 beta, IL-2 and TNF alpha production, and quantification of ROS. Natural killer activity, spontaneous lymphoproliferative response, IL-2, TNF alpha, IL-beta release and ROS production were increased after LPS injection. In conclusions, ROS and proinflammatory mediators produced by immune cells in response to LPS are involved in the oxidative stress of endotoxic shock. This oxidative state alters some functional characteristics of leukocytes (proliferation and NK activity).

The amount of thiolic antioxidant ingestion needed to improve several immune functions is higher in aged than in adult mice

With aging there is an increase of oxidative stress due to an imbalance between the oxidant production and the antioxidant levels in favor of the former. Since immune cell functions are specially linked to reactive oxygen species (ROS) generation, the oxidant/antioxidant balance is essential for these cells. Although low levels of antioxidants cause a decrease in immune function, very high levels of antioxidant compounds could show prooxidant effects. In the present work, we have studied the effect of diet supplementation, for 4 weeks, with two different doses of two thiolic antioxidants, namely thioproline (TP) and N-acetylcysteine (NAC), at 0.1% (w/w) and 0.3% (w/w, of each antioxidant) on the main immune system cells, i.e.: macrophages, lymphocytes and natural killer (NK) cells of adult (33+/-1 week old) and aged (75+/-1 week old) female Swiss mice. Two groups of animals, adult and aged mice, fed standard diet were used as controls. The results show that the ingestion of 0.1% doses of thiols improves, in the adult mice, several immune functions such as the chemotaxis capacity of both macrophages and lymphocytes, the phagocytosis of macrophages, the lymphoproliferative response to the mitogen Con A and the NK activity. Moreover, no change was observed in adherence capacity of immune cells, and superoxide production was decreased. By contrast, in aged mice the ingestion of these amounts of antioxidants did not change the immune functions studied with the exception of NK activity, which was stimulated. The ingestion of 0.3% of antioxidants by adult mice only increased some immune functions such as adherence and superoxide production, which are markers of oxidative stress. Other functions such as chemotaxis or lymphoproliferative response decreased. However, the ingestion of these very high amounts of thiols by aged animals increased the phagocytosis, the NK activity and specially the lymphoproliferative response to the mitogen, a function that is very depressed with aging.

Leukocyte function and life span in a murine model of premature immunosenescence

Aging associates with a decline of physiological functions, including the function of the nervous and the immune system. These aged-related changes occur in various degrees in different members of a mouse outbred population. Accordingly, we have proposed a model of premature immunosenescence in mice, based on the demonstration of premature decline in the behavioral response in a simple T-maze and in several immune functions in Swiss outbred mice. Those mice with a worst (slow) performance in this test (linked to a higher emotional response to stress) show a shorter life span and a decreased immune function when compared to fast mice. In order to provide biomarkers of "biological aging" related to health and survival, the present longitudinal study includes the analysis of several immunological parameters such as, proliferative response to mitogen Con A, NK activity and cytokine (TNFalpha, IL-1beta and IL-2) release by peritoneal leukocytes from female Swiss mice. Slow mice showed a lower proliferative response to Con A, IL-2 and IL-1beta release, an impaired NK activity and an increased TNFalpha production as compared to fast mice. Moreover, the age-associated decline of these functions is more strikingly slow than in fast mice. In summary, we propose the above immunological parameters, that change with aging at a different rate in members of a same population, as useful biomarkers to asses the rate of biological aging in mice.

Neuropeptide Y effects on murine natural killer activity: changes with ageing and cAMP involvement

Changes in the bidirectional interaction between the nervous and the immune systems have been proposed as a cause of ageing. Neuropeptides, such as neuropeptide Y (NPY), could show different effects on immune function with age. In the present work, we have studied the in vitro action of a wide range of NPY concentrations, i.e. from 10(-13) to 10(-7) M, on natural killer (NK) activity, a function which decreases with age. Spleen, axillary nodes, thymus and peritoneum leukocytes from mice of different ages: young (12+/-2 weeks), adult (24+/-2 weeks), mature (50+/-2 weeks) and old (72+/-2 weeks) were used. Stimulation by NPY of NK activity was observed in adult and mature animals in axillary nodes and thymus, and an inhibition in the spleen from young mice. The specificity of the NPY effect on cytotoxic activity was confirmed using a C-terminal fragment of NPY. Furthermore, cAMP levels in leukocytes were found to be decreased by NPY in adult mice, suggesting an involvement of this messenger system in the NK modulation by this neuropeptide.

Comparative study of peritoneal macrophage functions in mice receiving lethal and non-lethal doses of LPS

In previous studies, we have observed changes in several functions of peritoneal macrophages from female BALB/c mice with lethal endotoxic shock caused by intraperitoneal injection of Escherichia coli O55:B5 lipopolysaccharide (LPS; 100 mg/kg), which were associated with a high production of superoxide anion and tumor necrosis factor alpha (TNF-alpha). In the present work, both a lethal dose (250 mg/kg) and a non-lethal dose (100 mg/kg) of LPS were used in female Swiss mice. In peritoneal macrophages, the following functions were studied at 2, 4, 12 and 24 h after LPS injection: adherence to substrate, chemotaxis, ingestion of particles, and superoxide anion and TNF-alpha production. In both groups, the results showed a stimulation of adherence, ingestion and superoxide production as well as a decrease of chemotaxis, whereas TNF-alpha could not be detected in either of the two groups. These effects were more evident with the 250 mg/kg dose, especially as regards superoxide anion production, which was higher in the animals treated with a lethal dose of LPS.

Modulation of murine macrophage function by N-acetylcysteine in a model of endotoxic shock

In previous studies we have observed changes in several functions of peritoneal macrophages from BALB/c mice with irreversible endotoxic shock caused by intraperitoneal injection of E. coli lipopolysaccharide (LPS) (100 mg/kg), which were associated with a high production of superoxide anion. Since antioxidants, such as N-acetylcysteine (NAC), are free radical scavengers that improve the immune response, in the present work we have studied different functions of peritoneal macrophages from BALB/c mice suffering the endotoxic shock above indicated and administered N-acetylcysteine (150 mg/kg i.p.) at 30 minutes after LPS injection. In the peritoneal macrophages obtained at 2, 4, 12 and 24 h after LPS injection, the following functions were studied: adherence to substrate, mobility, ingestion of particles, and production of superoxide anion and tumour necrosis factor (TNF alpha). The increase in adherence, ingestion and superoxide anion and TNF alpha production shown by macrophages from animals with endotoxic shock was counteracted by NAC injection. Moreover, the survival time of mice with endotoxic shock was increased in the presence of NAC. These data suggest that NAC, administered intraperitoneally, may be useful for the treatment of irreversible endotoxic shock by modulation of the function of macrophages with decreased superoxide anion and TNF alpha production and concomitant increase of survival time.

Effects of endotoxic shock in several functions of murine peritoneal macrophages

Gram negative sepsis and septic shock continue to be a major medical problem, with a complex physiopathology and it is associated with high mortality. Although secretion of cytokines such as tumor necrosis factor-alpha by macrophages is the principal host mediator of septic shock, other characteristic functions of macrophages implicated in their phagocytic capacity have not been studied in the process of endotoxic shock. In the present study we have used an intraperitoneal injection of E. coli lipopolysaccharide (LPS) (100 mg/kg) in order to obtain an endotoxic shock model in adult female BALB/c mice. Peritoneal cell suspensions were obtained at several times (2, 4, 12 or 24 h) after injection and the following functions were studied on the peritoneal macrophages: adherence to substrate, mobility (spontaneous and directed or chemotaxis), ingestion of particles and superoxide anion production. The results showed a stimulation of adherence, ingestion and superoxide production as well as a decrease of chemotaxis in the animals injected with LPS. These effects changed with time after LPS injection. Thus, the increase of adherence and the decrease of mobility were higher during the first hours, whereas the increase in ingestion and superoxide production turned larger with time.