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The NADPARK study: A randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease.
Brakedal, B, Dölle, C, Riemer, F, Ma, Y, Nido, GS, Skeie, GO, Craven, AR, Schwarzlmüller, T, Brekke, N, Diab, J, et al
Cell metabolism. 2022;34(3):396-407.e6
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Plain language summary
Parkinson’s disease (PD) is a major cause of death and disability, and current treatments can provide partial symptomatic relief, mainly for motor symptoms but make no substantial impact on disease progression. A growing body of evidence supports that boosting cellular levels of nicotinamide adenine dinucleotide (NAD) may confer neuroprotective effects in both healthy aging and neurodegeneration. The primary aim of this study was to assess penetration and metabolic responses of the brain to nicotinamide riboside (NR) supplementation in patients with PD. This study is a double-blinded, randomised, placebo-controlled phase I study of NR in newly diagnosed PD patients, naïve to dopaminergic therapy. Participants (n=30) where randomly assigned (1:1) to one of the two groups: NR group or placebo group. Results show that: - oral NR therapy increases brain NAD levels and impacts cerebral metabolism in PD. - supplementation with NR may target multiple processes implicated in the pathophysiology of the disease by upregulating the expression of genes involved in mitochondrial respiration, oxidative damage response, lysosomal and proteasomal function and downregulating inflammatory cytokines in the central nervous system. Authors conclude that NR can be a potential neuroprotective agent against PD. However, further investigation in a larger trial is required to warrant these findings.
Abstract
We conducted a double-blinded phase I clinical trial to establish whether nicotinamide adenine dinucleotide (NAD) replenishment therapy, via oral intake of nicotinamide riboside (NR), is safe, augments cerebral NAD levels, and impacts cerebral metabolism in Parkinson's disease (PD). Thirty newly diagnosed, treatment-naive patients received 1,000 mg NR or placebo for 30 days. NR treatment was well tolerated and led to a significant, but variable, increase in cerebral NAD levels-measured by 31phosphorous magnetic resonance spectroscopy-and related metabolites in the cerebrospinal fluid. NR recipients showing increased brain NAD levels exhibited altered cerebral metabolism, measured by 18fluoro-deoxyglucose positron emission tomography, and this was associated with mild clinical improvement. NR augmented the NAD metabolome and induced transcriptional upregulation of processes related to mitochondrial, lysosomal, and proteasomal function in blood cells and/or skeletal muscle. Furthermore, NR decreased the levels of inflammatory cytokines in serum and cerebrospinal fluid. Our findings nominate NR as a potential neuroprotective therapy for PD, warranting further investigation in larger trials.
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Spexin peptide is expressed in human endocrine and epithelial tissues and reduced after glucose load in type 2 diabetes.
Gu, L, Ma, Y, Gu, M, Zhang, Y, Yan, S, Li, N, Wang, Y, Ding, X, Yin, J, Fan, N, et al
Peptides. 2015;71:232-9
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Little is known about the functions of the peptide spexin. Recent studies have shown a relationship between spexin and body weight regulation. It is thought that spexin might be related to glucose control and fat metabolism in type 2 diabetes mellitus (T2DM). The aim of this study was to examine the location of spexin in human tissue and measure spexin levels after a glucose load in T2DM patients. First, the researchers examined human tissue samples. Blood samples were then collected from 121 adults with T2DM and 105 healthy individuals. Additionally, an oral glucose tolerance test (OGTT) was performed on 12 healthy volunteers. In human tissue samples, the levels of spexin were highest in the adrenal gland, skin, stomach, small intestine, liver, thyroid, pancreatic islets, visceral fat, lung, colon, and kidney, and lowest in muscle and connective tissue. Blood levels of spexin were significantly lower in T2DM patients compared to healthy controls. Spexin levels were found to be inversely related to fasting blood glucose and lipids. During the OGTT, spexin levels were also inversely correlated with blood glucose levels. The authors concluded that spexin is highly expressed among endocrine and epithelial tissues. Changes in the blood levels of spexin could represent an adaptation to the rise of glucose and lipids associated with T2DM. However, the exact role of spexin in endocrine diseases is still to be discovered.
Abstract
Spexin mRNA and protein are widely expressed in rat tissues and associate with weight loss in rodents of diet-induced obesity. Its location in endocrine and epithelial cells has also been suggested. Spexin is a novel peptide that involves weight loss in rodents of diet-induced obesity. Therefore, we aimed to examine its expression in human tissues and test whether spexin could have a role in glucose and lipid metabolism in type 2 diabetes mellitus (T2DM). The expression of the spexin gene and immunoreactivity in the adrenal gland, skin, stomach, small intestine, liver, thyroid, pancreatic islets, visceral fat, lung, colon, and kidney was higher than that in the muscle and connective tissue. Immunoreactive serum spexin levels were reduced in T2DM patients and correlated with fasting blood glucose (FBG, r=-0.686, P<0.001), hemoglobin A1c (HbA1c, r=-0.632, P<0.001), triglyceride (TG, r=-0.236, P<0.001) and low density lipoprotein-cholesterol (LDL-C, r=-0.382, P<0.001). A negative correlation of blood glucose with spexin was observed during oral glucose tolerance test (OGTT). Spexin is intensely expressed in normal human endocrine and epithelial tissues, indicating that spexin may be involved in physiological functions of endocrine and in several other tissues. Circulating spexin levels are low in T2DM patients and negatively related to blood glucose and lipids suggesting that the peptide may play a role in glucose and lipid metabolism in T2DM.