Humanin: A Novel Central Regulator of Peripheral Insulin Action

Background

Decline in insulin action is a metabolic feature of aging and is involved in the development of age-related diseases including Type 2 Diabetes Mellitus (T2DM) and Alzheimer''s disease (AD). A novel mitochondria-associated peptide, Humanin (HN), has a neuroprotective role against AD-related neurotoxicity. Considering the association between insulin resistance and AD, we investigated if HN influences insulin sensitivity.

Methods and Findings

Using state of the art clamp technology, we examined the role of central and peripheral HN on insulin action. Continuous infusion of HN intra-cerebro-ventricularly significantly improved overall insulin sensitivity. The central effects of HN on insulin action were associated with activation of hypothalamic STAT-3 signaling; effects that were negated by co-inhibition of hypothalamic STAT-3. Peripheral intravenous infusions of novel and potent HN derivatives reproduced the insulin-sensitizing effects of central HN. Inhibition of hypothalamic STAT-3 completely negated the effects of IV HN analog on liver, suggesting that the hepatic actions of HN are centrally mediated. This is consistent with the lack of a direct effect of HN on primary hepatocytes. Furthermore, single treatment with a highly-potent HN analog significantly lowered blood glucose in Zucker diabetic fatty rats. Based upon the link of HN with two age-related diseases, we examined if there were age associated changes in HN levels. Indeed, the amount of detectable HN in hypothalamus, skeletal muscle, and cortex was decreased with age in rodents, and circulating levels of HN were decreased with age in humans and mice.

Conclusions

We conclude that the decline in HN with age could play a role in the pathogenesis of age-related diseases including AD and T2DM. HN represents a novel link between T2DM and neurodegeneration and along with its analogues offers a potential therapeutic tool to improve insulin action and treat T2DM.     

Intranasal Odorant Concentrations in Relation to Sniff Behavior

Knowledge on how odorants are transported through the nasal cavity to the olfactory epithelium is limited. One facet of this is how the sniffing behavior affects the abundance of odorants transferred to the olfactory cleft and in turn influences odor perception. A novel system that couples an online mass spectrometer with an odorant pulse delivery olfactometer was employed to characterize intranasal odorant concentrations of butane‐2,3‐dione (or butanedione, commonly known as diacetyl) at the interior naris and the olfactory cleft. Volunteers (n=12) were asked to perform different modes of sniffing in relation to the sniff intensity that were categorized as ‘normal’, ‘rapid’ and ‘forced’. The highest concentrations of butanedione at both positions in the nose were observed during normal sniffing, with the lowest concentrations correlating with periods of forced sniffs. This corresponded to the panelists' ratings that normal sniffing elicited the highest odor intensities. These feasibility assessments pave the way for more in‐depth analyses with a variety of odorants of different chemical classes at various intranasal positions, to investigate the passage and uptake of odorants within the nasal cavity.     

Immunogenicity of Intensively Decellularized Equine Carotid Arteries Is Conferred by the Extracellular Matrix Protein Collagen Type VI

The limited biocompatibility of decellularized scaffolds is an ongoing challenge in tissue engineering. Here, we demonstrate the residual immunogenicity of an extensively decellularized equine carotid artery (dEAC_intens) and identify the involved immunogenic components. EAC were submitted to an elaborated intensified decellularization protocol with SDS/sodium desoxycholate for 72 h using increased processing volumes (dEAC_intens), and compared to dEAC_ord prepared by an ordinary protocol (40 h, normal volumes). Matrix integrity was checked via correlative volumetric visualization which revealed only minor structural changes in the arterial wall. In dEAC_intens, a substantial depletion of cellular components was obvious for smooth muscle actin (100%), MHC I complexes (97.8%), alphaGal epitops (98.4% and 91.3%) and for DNA (final concentration of 0.34±0.16 ng/mg tissue). However, dEAC_intens still evoked antibody formation in mice after immunization with dEAC_intens extracts, although to a lower extent than dEAC_ord. Mouse plasma antibodies recognized a 140 kDa band which was revealed to contain collagen VI alpha1 and alpha2 chains via mass spectrometry of both 2D electrophoretically separated and immunoprecipitated proteins. Thus, even the complete removal of cellular proteins did not yield non-immunogenic dEAC as the extracellular matrix still conferred immunogenicity by collagen VI. However, as lower antibody levels were achieved by the intensified decellularization protocol, this seems to be a promising basis for further development.     

Perinatal Exposure of Mice to the Pesticide DDT Impairs Energy Expenditure and Metabolism in Adult Female Offspring

Dichlorodiphenyltrichloroethane (DDT) has been used extensively to control malaria, typhus, body lice and bubonic plague worldwide, until countries began restricting its use in the 1970s. Its use in malaria control continues in some countries according to recommendation by the World Health Organization. Individuals exposed to elevated levels of DDT and its metabolite dichlorodiphenyldichloroethylene (DDE) have an increased prevalence of diabetes and insulin resistance. Here we hypothesize that perinatal exposure to DDT disrupts metabolic programming leading to impaired metabolism in adult offspring. To test this, we administered DDT to C57BL/6J mice from gestational day 11.5 to postnatal day 5 and studied their metabolic phenotype at several ages up to nine months. Perinatal DDT exposure reduced core body temperature, impaired cold tolerance, decreased energy expenditure, and produced a transient early-life increase in body fat in female offspring. When challenged with a high fat diet for 12 weeks in adulthood, female offspring perinatally exposed to DDT developed glucose intolerance, hyperinsulinemia, dyslipidemia, and altered bile acid metabolism. Perinatal DDT exposure combined with high fat feeding in adulthood further impaired thermogenesis as evidenced by reductions in core temperature and in the expression of numerous RNA that promote thermogenesis and substrate utilization in the brown adipose tissue of adult female mice. These observations suggest that perinatal DDT exposure impairs thermogenesis and the metabolism of carbohydrates and lipids which may increase susceptibility to the metabolic syndrome in adult female offspring.     

Frequent Seizures Are Associated with a Network of Gray Matter Atrophy in Temporal Lobe Epilepsy with or without Hippocampal Sclerosis

Objective

Patients with temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS) have diffuse subtle gray matter (GM) atrophy detectable by MRI quantification analyses. However, it is not clear whether the etiology and seizure frequency are associated with this atrophy. We aimed to evaluate the occurrence of GM atrophy and the influence of seizure frequency in patients with TLE and either normal MRI (TLE-NL) or MRI signs of HS (TLE-HS).

Methods

We evaluated a group of 172 consecutive patients with unilateral TLE-HS or TLE-NL as defined by hippocampal volumetry and signal quantification (122 TLE-HS and 50 TLE-NL) plus a group of 82 healthy individuals. Voxel-based morphometry was performed with VBM8/SPM8 in 3T MRIs. Patients with up to three complex partial seizures and no generalized tonic-clonic seizures in the previous year were considered to have infrequent seizures. Those who did not fulfill these criteria were considered to have frequent seizures.

Results

Patients with TLE-HS had more pronounced GM atrophy, including the ipsilateral mesial temporal structures, temporal lobe, bilateral thalami and pre/post-central gyri. Patients with TLE-NL had more subtle GM atrophy, including the ipsilateral orbitofrontal cortex, bilateral thalami and pre/post-central gyri. Both TLE-HS and TLE-NL showed increased GM volume in the contralateral pons. TLE-HS patients with frequent seizures had more pronounced GM atrophy in extra-temporal regions than TLE-HS with infrequent seizures. Patients with TLE-NL and infrequent seizures had no detectable GM atrophy. In both TLE-HS and TLE-NL, the duration of epilepsy correlated with GM atrophy in extra-hippocampal regions.

Conclusion

Although a diffuse network GM atrophy occurs in both TLE-HS and TLE-NL, this is strikingly more evident in TLE-HS and in patients with frequent seizures. These findings suggest that neocortical atrophy in TLE is related to the ongoing seizures and epilepsy duration, while thalamic atrophy is more probably related to the original epileptogenic process.     

Isolation,characterization and analysis of the agglutinative activity of a lectin from <Emphasis Type="Italic">Crotalaria spectabilis</Emphasis>

Lectins are proteins with ability to recognize specific carbohydrates. These are present in virtually all organisms and have increasing applications in biotechnology. Here, our aim was to purify lectins from seeds of Crotalaria spectabilis Roth and determine their agglutinative ability. In this study, 45 g of seeds were milled, their proteins were precipitated by acetone or ammonium sulfate and purified by exclusion and ion-exchange chromatography. An isolated lectin was submitted to tests for hemagglutination and inhibition of hemagglutinating activity by carbohydrates as well as tests for its response to chelating and reducing agents. Our results show that the apparent molecular weight (as determined by SDS-PAGE) of the lectin is 30 kDa, and the tests for inhibition of erythrocytes’ agglutinative activity by sugars were positive for d-galactose and N-acetyl-d-galactosamine. Data obtained with the chelating agent EDTA demonstrated the presence of divalent cations in the protein structure. However, the reducing agent 2-mercaptoethanol was unable to inhibit the protein’s bioactivity. The lectin agglutinated the blood groups A, B, AB and O, as well as bacterial lineages from the species Leptospira interrogans and Leptospira biflexa, indicating a prospective application in the diagnosis and treatment of leptospirosis.