Effects of Streptozotocin Induced Diabetes on One-Carbon Cycle and Sperm Function

OBJECTIVE

Diabetic men suffer an increased risk of infertility associated with signs of oxidative damage and decreased methylation in sperm pointing to a deficit of the one-carbon cycle (1CC). We aimed to investigate this deficit using mice models (type 1 and 2) of streptozotocin-induced diabetes.

MATERIALS AND METHODS

In this experimental study, 50 male mice, aged eight weeks, were divided randomly into four groups: sham, control, type 1 diabetes mellitus (DM1), and DM2. The DM1 group was fed a normal diet (ND) for eight weeks, followed by five consecutive days of intraperitoneal administration of Streptozotocin (STZ, 50 mg/kg body weight). The DM2 group was fed a high-fat diet (HFD) for eight weeks, followed by a single intraperitoneal injection of STZ (100 mg/kg). After twelve weeks, all the mice were euthanized, and study parameters assessed. In the sham group, citrate buffer as an STZ solvent was injected.

RESULTS

Both types of diabetic animals had serious impairment of spermatogenesis backed by increased DNA damage (P=0.000) and decreased chromatin methylation (percent: P=0.019; intensity: P=0.001) and maturation (P=0.000). The 1CC was deeply disturbed with increased homocysteine (P=0.000) and decreased availability of carbon units [methionine (P=0.000), serine (P=0.088), folate (P=0.016), B12 (P=0.025)] to feed methylations.

CONCLUSION

We have observed a distinct impairment of 1CC within the testes of individuals with diabetes. We speculate that this impairment may be linked to inadequate intracellular glucose and diminished carbon unit supply associated with diabetes. As a result, interventions focusing on enhancing glucose uptake into sperm cells and providing supplementary methyl donors have the potential to improve fertility issues in diabetic patients. However, additional clinical testing is required to validate these hypotheses.

Micronutrients of the one-carbon metabolism cycle are altered in mothers and neonates by gestational diabetes and are associated with weight, height and head circumference at birth

While several studies have previously described the levels of one-carbon metabolism-related micronutrients in women with gestational diabetes mellitus (GDM) and their neonates, the results in these literature reports have been contradictory. We hypothesized that the concentrations of micronutrients involved in the one-carbon cycle are altered in pregnant women and their neonates by GDM, and that these changes could further modify the neonatal anthropometry. Micronutrient levels were measured in 123 pregnant women with normal glucose levels (M-ND) and their neonates (N-ND), as well as in 54 pregnant women with gestational diabetes (M-GDM) and their neonates (M-GDM). Folate and vitamin B12 levels were measured via competitive ELISA, and betaine, choline, and glycine levels were measured via ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS). Vitamin B12 and Glycine were found to be higher in M-GDM compared to M-ND. N-GDM had higher levels of folic acid and vitamin B12 and lower levels of betaine and choline compared to N-ND. In general, neonates presented with high concentrations of micronutrients compared to their mothers, and the fetus/maternal ratio of micronutrients was higher among the N-ND as compared to the N-GDM. Micronutrients were also variably associated with anthropometric measurements. The association of betaine with neonatal anthropometry in N-GDM is highlighted. In summary, our results implicate a potential role of GDM in altering the levels of one-carbon metabolism-related micronutrients among pregnant women and their neonates. Likewise, our results also elucidate a potential association between the concentrations of micronutrients and the weight, height, and head circumference of neonates.

Alterations in folate-dependent one-carbon metabolism as colon cell transition from normal to cancerous

Folate-dependent one-carbon cycle metabolism (FOCM) plays a critical role in maintaining genomic stability through regulating DNA biosynthesis, repair and methylation. Folate metabolites as well as other metabolites in the FOCM are hypothesized to be altered when cells transition from normal to cancerous state. Using cells at different stages in their development into colorectal cancer, the FOCM metabolites were profiled as an effort to phenotype the cells, and the metabolite levels were compared to the expressions of related genes. Here, we investigate whether there is a correlation between the metabolite levels, DNA methylation levels and the expression of the related genes that drive the levels of these metabolites. Using CRL1459, APC10.1, HCT116 and Caco-2, we show for the first time that FOCM metabolites correlate with the gene expression patterns. These differences follow a trend that may facilitate distinguishing colon cells at the different stages as they transition into cancerous state. The folate distribution and methionine levels were found to be key in determining the staging of the colon cells in CRC development. Also, expression of CBS, MTRR and MAT genes may facilitate distinguishing between untransformed and transformed colon cells.

Short term methionine restriction increases hepatic global DNA methylation in adult but not young male C57BL/6J mice

Despite well-documented evidence for lifespan extension by methionine restriction (MR), underlying mechanisms remain unknown. As methionine can alter S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH), the substrate and product of DNA methyltransferase-1 (DNMT1), we hypothesized that MR diet alters DNA methylation. Young (8-week-old) and adult (1-year-old) male C57BL/6J mice were fed diets with different levels of methionine (0.12%-MR, 0.84%-CD) for 12weeks. Functional indicators of DNA methylation, including global methylation (GM), gene-specific methylation (GSM) and LINE-1 methylation; and biochemical factors affecting DNA methylation, SAH, SAM, and DNMT1 were assessed in different tissues. MR altered DNA methylation depending on the age of intervention. While MR had no effect on hepatic GM in young animals, it increased GM by 27% over CD in adults (p<0.01). In comparison with young animals, hepatic GM levels were 17% lower in CD adults (p<0.05), but not different in MR adults. The MR-induced increase in hepatic GM was associated with a 38% decrease in SAH levels in adults (p<0.001), with SAH and GM levels being negatively correlated (r²=0.33, p<0.001). No changes were observed in DNMT protein levels in liver. In adipose tissue, MR caused a 6% decline in GM in adults (p<0.05), a corresponding 2-fold increase in SAH (p<0.05), and a 2-fold decrease in DNMT1 (p<0.01). MR caused both increases and decreases in GSM of liver and adipose. No changes were observed in LINE-1. Together, these findings provide evidence for protective effects of MR diet on hepatic DNA hypomethylation in adults, apparently mediated by SAH. These findings also indicate that altered DNA methylation might be playing a role in benefits conferred by MR diet.

Erythrocyte fatty acid profiles and plasma homocysteine, folate and vitamin B6 and B12 in recurrent depression: Implications for co-morbidity with cardiovascular disease

Oxidative stress induced interactions between fatty acid (FA) and one-carbon metabolism may be involved in co-occurrence of major depressive disorder (MDD) and cardiovascular disease (CVD), which have been scarcely studied together. In 137 recurrent MDD-patients vs. 73 age- and sex-matched healthy controls, we simultaneously measured key components of one-carbon metabolism in plasma (homocysteine, folate, vitamins B6 and B12), and of FA-metabolism in red blood cell membranes [main polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA) and structural FA-indices (chain length, unsaturation, peroxidation)]. Results show significant positive associations of folate with EPA, DHA, and the peroxidation index, which were similar in patients and controls. After correction for confounders, these associations were lost except for EPA. Associations between B-vitamins and FA-parameters were non-significant, but also similar in patients and controls. Homocysteine and DHA were significantly less negatively associated in patients than in controls. In conclusion, these data indicate similarities but also differences in associations between parameters of one-carbon and FA-metabolism in recurrent MDD patients vs. controls, which may reflect differences in handling of oxidative stress. Further research should test the consequences of these differences, particularly the premature development of CVD in MDD.

Methylating micronutrient supplementation during pregnancy influences foetal hepatic gene expression and IGF signalling and increases foetal weight

PURPOSE

Maternal diet during pregnancy impacts foetal growth and development. In particular, dietary levels of methylating micronutrients (methionine, folate, choline, vitamins B6, and B12) interfere with the availability and allocation of methyl groups for methylation reactions, thereby influencing normal transcription. However, the currently recommended methylating micronutrient supplementation regimen is haphazard and arbitrary at best.

METHODS

To investigate the effects of a methylating micronutrient-rich maternal diet, pregnant Pietrain sows were fed either a standard diet (CON) or a diet supplemented with methionine, folate, choline, B6, B12, and zinc (MET). Foetal liver and muscle (M. longissimus dorsi) tissues were collected at 35, 63, and 91 days post-conception. Transcriptional responses to diet were assessed in foetal liver. Altered insulin-like growth factor (IGF) signalling in transcriptome analyses prompted investigation of IGF-2 and insulin-like growth factor binding proteins (IGFBPs) levels in muscle and liver.

RESULTS

Maternal diet enriched with methylating micronutrients was associated with increased foetal weight in late gestation. Hepatic transcriptional patterns also revealed differences in vitamin B6 and folate metabolism between the two diets, suggesting that supplementation was effective. Additionally, shifts in growth-supporting metabolic routes of the lipid and energy metabolism, including IGF signalling, and of cell cycle-related pathways were found to occur in liver tissue in supplemented individuals. Weight differences and modulated IGF pathways were also reflected in the muscle content of IGF-2 (increased in MET) and IGFBP-2 (decreased in MET).

CONCLUSIONS

Maternal dietary challenges provoke stage-dependent and tissue-specific transcriptomic modulations in the liver pointing to molecular routes contributing to the organismal adaptation. Subtle effects on late foetal growth are associated with changes in the IGF signalling mainly in skeletal muscle tissue that is less resilient to dietary stimuli than liver.

S-adenosyl methionine (SAMe) versus escitalopram and placebo in major depression RCT: efficacy and effects of histamine and carnitine as moderators of response

OBJECTIVE

To assess the antidepressant efficacy of S-adenosyl methionine (SAMe), a naturally occurring methyl donor, versus the selective serotonin reuptake inhibitor (SSRI) escitalopram and a placebo control; and to determine whether serum histamine or carnitine levels modified treatment response.

METHODS

We examined a subsample (n=144) from one site of a two-site study of adults with diagnosed Major Depressive Disorder (MDD), recruited from 4/13/05 to 12/22/09, who consented to the additional blood draw for serum histamine and carnitine levels. After washout, eligible subjects were randomized to SAMe (1600-3200mg/daily), escitalopram (10-20mg/daily), or matching placebo for 12 weeks of double-blind treatment (titration at week 6 in non-response).

RESULTS

On the primary outcome of the Hamilton Depression Rating Scale (HAMD-17), a significant difference in improvement was observed between groups from baseline to week 12 (p=0.039). The effect size from baseline to endpoint was moderate to large for SAMe versus placebo (d=0.74). SAMe was superior to placebo from week 1, and to escitalopram during weeks 2, 4, and 6. No significant effect was found between escitalopram and placebo or SAMe. Response rates (HAMD-17≥50% reduction) at endpoint were 45%, 31%, and 26% for SAMe, escitalopram, and placebo, respectively; while remission rates (HAM-D≤7) were 34% for SAMe (p=0.003), 23% for escitalopram (p=0.023), and 6% for placebo. No correlation between baseline histamine level and reduction of HAMD-17 score was found for either the SAMe or escitalopram groups. Baseline carnitine levels were also not found to moderate response to either treatment.

LIMITATIONS

While SAMe appears to be an effective antidepressant agent, the overall findings from the parent study (which showed no significant difference between groups due to site differences) must be taken into consideration.

CONCLUSIONS

These preliminary results provide encouraging evidence for the use of SAMe in the treatment of MDD. Histamine and carnitine serum level may not necessarily moderate response to SAMe.