Nicotinamide Mononucleotide, an NAD+ Precursor, Rescues Age-Associated Susceptibility to AKI in a Sirtuin 1–Dependent Manner

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The rapid growth of an aging population creates challenges regarding age-related diseases, including AKI, for which both the prevalence and death rate increase with age. The molecular mechanism by which the aged kidney becomes more susceptible to acute injury has not been completely elucidated. In this study, we found that, compared with the kidneys of 3-month-old mice, the kidneys of 20-month-old mice expressed reduced levels of the renal protective molecule sirtuin 1 (SIRT1) and its cofactor NAD+. Supplementation with nicotinamide mononucleotide (NMN), an NAD+ precursor, restored renal SIRT1 activity and NAD+ content in 20-month-old mice and further increased both in 3-month-old mice. Moreover, supplementation with NMN significantly protected mice in both age groups from cisplatin-induced AKI. SIRT1 deficiency blunted the protective effect of NMN, and microarray data revealed that c-Jun N-terminal kinase (JNK) signaling activation associated with renal injury in SIRT1 heterozygotes. In vitro, SIRT1 attenuated the stress response by modulating the JNK signaling pathway, probably via the deacetylation of a JNK phosphatase, DUSP16. Taken together, our findings reveal SIRT1 as a crucial mediator in the renal aging process. Furthermore, manipulation of SIRT1 activity by NMN seems to be a potential pharmaceutical intervention for AKI that could contribute to the precise treatment of aged patients with AKI.


It is well documented that the incidence of AKI increases with age.1,2 Multiple studies have shown that aging is an independent risk factor for AKI and its associated mortality and morbidity.1–4 Although aging-associated comorbidities and iatrogenic factors are responsible for these outcomes, age-related cellular deterioration and an impaired response of the renal cells to stress have also been recognized to increase the susceptibility of the kidney to injury.5–8

Recent studies have shown that sirtuin 1 (SIRT1) plays an important role in the cellular response to stress and has been shown to extend the lifespan, at least in lower animals.9–11 SIRT1, an NAD+-dependent deacetylase, is a member of the Sirtuin family, which has seven family members. SIRT1 is primarily localized to the nucleus, where it deacetylates many nuclei proteins and transcription factors. SIRT1 has been shown to underlie calorie restriction–related health benefits, including prolonged lifespan and reduced age-related deterioration.12–14 Consistently, activators of SIRT1, including resveratrol and synthetic SIRT1–activating compounds, have been shown to promote health in experimental animals,15–18 although the results from human studies are somewhat variable, probably because of the complexities of the mechanisms of their action.19–22

NAD+ is known to mediate hydrogen transfer in the intracellular metabolic pathway in mitochondria and the redox reaction. NAD+ has also been found to be an indispensable cofactor for several important enzymatic reactions, including SIRT1, supporting an important role of SIRT1 in modulating the cellular response to metabolism and oxidative stress.23–25 Accumulation studies suggest that cellular NAD+ levels reduce with aging26–28 and are accompanied by reduced SIRT1 activity.5,14 Boosting NAD+ is associated with lifespan extension,26,29 and restoring NAD+ with NAD+ precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside, corrects many metabolic abnormalities.30–33

In this study, we examined the role of NAD+/SIRT1 in the susceptibility to AKI in aged animals. Our study shows that NAD+ and SIRT1 deficits in aged mice kidneys contributed to increased vulnerability to cisplatin-induced AKI; NMN treatment rescued the aged kidneys from cisplatin-induced AKI in an SIRT1-dependent manner. The mechanism by which NAD+/SIRT1 protects the kidney involves epigenetic regulation of the c-Jun N-terminal kinase (JNK) pathway. This study sheds light on the mechanisms underlying age-associated susceptibility to AKI and identifies endogenous NAD+ as a potential therapeutic target for AKI, particularly in the elderly.



The Effect of NMN Is Dependent on SIRT1

To determine whether the protective effect of NMN depends on SIRT1, we examined the effect of NMN on SIRT1-deficient mice and also, equivalently damaged wild-type mice treated with higher dose of cisplatin (30 mg/kg body wt) (Supplemental Figure 3). As shown in Figure 6 and Supplemental Figure 4, NMN protected the kidney from severe renal injury in wildtype mice, but this therapeutic effect was substantially attenuated when one allele of the SIRT1 gene was deleted. Consistent in vivo data also supported that NMN rescued cisplatininduced cell death in a SIRT1-dependent manner.

Figure 1. Aging worsens acute kidney injury induced by cisplatin. Renal function evaluated by (A) BUN and (B) serum creatinine in the indicated groups at 72 hours after saline or cisplatin treatment (n=5 for saline-treated groups and n=8 for cisplatin-treated groups). (C) Tissue damage scored by the percentage of damaged tubules in cisplatinor saline-treated 3and 20-month-old mouse kidneys (n=6). (D) Representative hematoxylin and eosin–stained sections at both low and high magnification. (E) EM examination of renal PTCs in the indicated groups is shown and quantified. Data are expressed as mean6SEM and were analyzed using unpaired Student’s t test between two groups and ANOVA between multiple groups followed by post-tests. Scale bars, 2 mm. *P,0.05; **P,0.01.

Figure 2. Decreased SIRT1 expression and NAD+ levels in the aged kidney. (A) Relative mRNA expression of SIRT1 in the kidney cortex of 3and 20-month-old 129 mice (n=6). (B) Representative Western blotting image of SIRT1 protein expression in the kidney cortex. b-Actin was used as the loading control. (C) NAD+ level and (D) the relative mRNA expression of NAMPT, NMNAT1, and NMNAT3 in kidney cortexes of 3and 20-month-old 129 mice (n=6). Data are expressed as mean6SEM and were analyzed by unpaired Student’s t test. *P,0.05; ****P,0.001.

NMN Treatment Benefits Kidney from IschemiaReperfusion Injury

We further verified the therapeutic effect of NMN in an additional AKI model; 22 minutes of bilateral renal ischemia was induced in wild-type mice, and NMN or PBS was administrated before the surgery and 24 hours after reperfusion. Kidney function and histology analysis were performed at 48 hours after reperfusion. As shown in Figure 7, mice treated with NMN had much lower BUN and serum creatinine levels and improved tubular damage compared with mice treated with PBS. Therefore, beneficial effects of NMN on kidney were shown in both cisplatinand ischemia-reperfusion–induced AKI, indicating endogenous NAD+ as a potential target for AKI treatment.

The JNK Signaling Pathway Is Activated in Age-Associated AKI

A microarray study was conducted to explore the molecular mechanism involved in age-associated susceptibility to AKI. Renal cortex samples of SIRT1-intact or -deficient mice subjected to cisplatin or saline as the control were assigned in the mRNA microarray. Each group contained three biologic duplicates. Extensive pathway-network analysis of the array data pointed to MAPK/JNK signaling being responsible for increased acute renal injury in the absence of one allele of

SIRT1 (Supplemental Figure 5). The microarray data were validated by Western blotting of the three main signaling modules in the MAPK pathway. JNK other than p38 or extracellular signal–regulated kinase 1/2 (ERK1/2) showed a robust activation via the enhanced phosphorylation of JNK as well as c-JUN and ATF2 (Figure 8A). In addition, JNK signaling activation was observed in the age-associated injured kidney (Figure 8B).

The JNK Inhibitor Prevents Cisplatin-Induced Apoptosis in Cultured HK-2 Cells

To determine whether JNK activation was associated with SIRT1 deficiency–enhanced cell injury, we examined the effect of JNK inhibitor on cell survival and apoptosis in cells deficient in SIRT1. Consistent with SIRT1 knockout mice, knocking down SIRT1 by siRNA in cultured HK-2 cells sensitized the cells to cisplatin (Figure 9, A and B). Transfection with SIRT1 siRNA or scrambled RNA HK-2 cells showed signs of apoptosis and the phosphorylation of JNK after exposure to cisplatin. Cell viability was decreased and cleaved caspase-3 protein expression was enhanced in cisplatin-treated SIRT1 knockdown cells compared with the control. SP600125, a JNK inhibitor, blocked JNK activation and reduced apoptosis in cisplatin-treated HK-2 cells (Figure 9, A and B). Interestingly, in addition to the protective effect of the JNK inhibitor on HK-2 cells from cisplatin-induced apoptosis, we

Figure 3. NMN supplementation is associated with SIRT1 activation. (A) NAD+ content and (B) the enzymatic activity of SIRT1 in the kidney cortexes of 3and 20-month-old mice given PBS or NMN (n=5–6 for PBS-treated groups and n=3–6 for NMN-treated groups). (C) Western blotting of the acetylation of Foxo1 was performed to assess the enzymatic activity of SIRT1 in the kidney cortex. GAPDH protein expression was used as the loading control. Data are expressed as mean6SEM and were analyzed by ANOVA between multiple groups followed by post-tests. *P,0.05; **P,0.01; ***P,0.001.


The relationship between the loss of SIRT1 and the activation of JNK was further examined using two SIRT1 siRNAs targeting different loci of the SIRT1 gene. Transfected with either of these two siRNAs for 48 hours, SIRT1 protein expression was suppressed in HK-2 cells (Figure 9C). JNK was phosphorylated and activated as indicated by Western blotting, which revealed the phosphorylation of ATF2. Because no direct interaction between SIRT1 and JNK was detected in the immunoprecipitation experiment (data not shown), we examined the upstream phosphor-kinase and phosphatase of JNK, because JNK signaling is a phosphorylation-dependent cascade. We investigated MKK7 and MKK4, two major JNK-phosphorkinases, both in the total and phosphorylated form of MKK7 and MKK4 and found no alteration in the deprivation of SIRT1 (Figure 9C). To explore the related phosphatase levels, we constructed a flag-tagged dual-specificity phosphatase16 (DUSP16) plasmid and delivered it into HK-2 cells with SIRT1 siRNA or scrambled RNA, and the phosphorylation and acetylation levels of flag-DUSP16 were determined by immunoprecipitation. When SIRT1 was silenced by siRNA, the phosphorylation of flag-DUSP16 was downregulated, whereas acetylation was upregulated (Figure 9D). Additionally, in HK-2 cells, SIRT1 was coprecipitated with DUSP16 and was not coprecipitated with other JNK phosphatases and phosphor-kinases (Figure 9E). The interaction between SIRT1 and DUSP16 was further confirmed by reverse IP, in which flag-DUSP16 was found to be coprecipitated with SIRT1 (Figure 9F, Supplemental Figure 6A). This finding strongly suggested that, with the lack of SIRT1, DUSP16 would remain acetylated instead of becoming phosphorylated and lose its phosphatase activity, resulting in a constant phosphorylation of JNK. Additional experiment using lysine to arginine mutant DUSP16 plasmids identified lys462 and lys482 as acetylated targets of DUSP16, because SIRT1 deficiency– induced JNK phosphorylation was blunted in HK-2 cells when transfected with lys462 and lys482 mutant DUSP16 plasmid (Supplemental Figure 6B).



Complex factors contribute to the enhanced susceptibility to AKI with age.3–5,36,37 Comorbidities, such as diabetes, hypertension, hyperlipidemia, vascular diseases, and iatrogenic

factors, such as contrast, medication, and surgical procedures, all may contribute to age-associated susceptibility to AKI. Our previous studies and those of others have shown that the longevity gene SIRT1 plays a critical role in protecting the kidney from injury.5,38–41 This study identified the substrate of SIRT1, NAD+, as an important factor associated with increased susceptibility to AKI among the elderly. We showed that aged kidneys have decayed NAD+ metabolism and reduced SIRT1, and supplementation of NMN, an NAD+ precursor, restored the NAD+ content and SIRT1 activity and rescued cisplatin-induced acute renal damage. SIRT1 deficiency substantially blunted the protective effect of NMN, indicating that the renal protective effect of NMN relied on SIRT1. Thus, increasing endogenous NAD+ levels could become a therapeutic target for AKI, particularly in the elderly.

A reduced level of NAD+ has been detected with aging in worms, skeletal muscles and livers in mice, and skin tissues in human,26–28 although the mechanism remains unclear. The salvage pathway accounts for most of the NAD+ in mammals, which is catalyzed by two rate-limiting enzymes. Briefly, NAD+ is converted from NMN by NMNAT after the conversion of NMN from nicotinamide by NAMPT.34 Thus, a deficit in the salvage pathway could contribute to the insufficient production of NAD+.42 Overconsumption would also cause NAD+ deficiency. PARPs and CD38, two NADases, also use NAD+ as a substrate, thus consuming NAD+. PARP-1 knockout is associated with elevated NAD+ levels.43 During aging, activated PARP-1 due to increased DNA damage has been suggested to contribute to reduced NAD+ levels in aged organs.32,33 A recent study revealed that CD38 level and activity increased in multiple tissues during aging and played an important role in ageassociated NAD+ decline.44 In this study, the message RNA expression levels of both NAMPT and NMNAT were lower in the kidney cortex of 20-month-old mice compared with that in 3-month-old mice, indicating that the decline of the NAD+ expressed in proliferating cells and tissues,45 suggesting that the NMNAT might be decreased as an adaptive response to the reduced metabolism in the aged animals. Notably, two of three isoforms of NMNATs are found in the kidney: NMNAT1, mainly expressed in the nucleus, and NMNAT3, expressed in the mitochondria. Shrinkage of the NAD+ pool in the nucleus and mitochondria during aging was suggested indirectly by decreased NMNAT1 and NMNAT3 expression, but the precise subcellular distribution and alteration of the NAD+ content are not clear. Given that NAD+ is able to travel freely inside the cell, decreased cellular NAD+ levels may result in reduced activity of the enzymes that use NAD+ as a substrate, including SIRT1. This study shows that NMN, an intermediate product of NAD+ biosynthesis in the salvage pathway, replenished NAD+ levels in the aged kidneys and benefited the kidney with cisplatin-induced AKI, suggesting that reduced NAD+ levels are associated with enhanced kidney injury and that NAD+ may be an important intervention target for kidney protection.

NAD+ is required for SIRT1 activity, and SIRT1 has been previously documented as a renal survival factor.38 We examined whether the protective effect of NMN depended on SIRT1. This study shows that the intraperitoneal injection of NMN boosted NAD+ levels in both young and aged kidneys, which was also associated with increased activity of SIRT1, and protected the kidneys from both cisplatinand ischemia-reperfusion–induced AKI, indicating that NMN rescued AKI by activating SIRT1. Importantly, the protective effect of NMN supplementation was substantially blunted in SIRT1-deficient mice, indicating that the protective effect of NMN occurs through SIRT1 activity.


The mechanism by which SIRT1 exerts its health benefit has been extensively studied. FOXO, PGC1a, NF-kB, and HIF have been reported to be targets of SIRT1.46 To define the signaling mechanism underlying SIRT1 deficiency–associated AKI, we applied the microarray approach using SIRT1deficient or -intact mice exposed to cisplatin or the vehicle.


The array data indicated the activation of JNK signaling. Activation of JNK was then validated through Western blotting. Because JNK phosphorylation is observed in injured tissue, to examine whether the JNK activation is caused by tissue damage, we induced similar kidney injuries among wildtype mice (30 mg/kg cisplatin) and SIRT1-deficient mice (20 mg/kg) and found more intensive JNK phosphorylation in the heterozygotes than in the wild-type mice, indicating that the JNK activation was enhanced by SIRT1 deficiency (Supplemental Figure 3). Additionally, the administration of a JNK inhibitor attenuated cisplatin-induced apoptosis in both SIRT1-intact and -deficient HK-2 cells. In the cell culture study, JNK activation was observed when SIRT1 was knocked down by siRNA in HK-2 cells.

We then examined the mechanism by which SIRT1 influences JNK. Our IP experiment failed to find a direct interaction of SIRT1 and JNK. We then examined the phosphor-kinase and phosphatases of JNK and found that DUSP16 is a potential target of SIRT1. DUSP16, belonging to a family of mitogen-activated protein kinase phosphatases (MKPs), shows a specificity preference for JNK.47 MKPs are inducible and act rapidly as a feedback loop of the MAPK cascade in a cell type–specific manner.48 Furthermore, MKPs can be modified post-transcriptionally. In HK-2 cells transfected with SIRT1 siRNA, we found an enhanced acetylation and reduced phosphorylation of DUSP16. Given that SIRT1 is a deacetylase and targets a variety of proteins in addition to histones, it is plausible that acetylated DUSP16 was present in the absence of SIRT1. More importantly, interaction between SIRT1 and DUSP16 was observed in HK-2 and 293T cells by coimmunoprecipitation. It has been documented that the phosphorylated state of MKPs is associated with their stabilization and prolonged half-life49; therefore, the reduction of phosphorylated DUSP16 in SIRT1 deprivation may reduce their phosphatase activity and lead to the sustained activation of JNK. Two lysines (lys462 and lys482) are closely located near the phosphorylated site, serine446 of the DUSP16 protein, prompting the possibility that acetylation might compete with phosphorylation and influence protein functioning under certain circumstances.

In summary, renal aging is associated with declined NAD+ metabolism and the consequent reduced SIRT1 activity and increased susceptibility to AKI. Supplementation with NMN, an NAD+ precursor, restores NAD+ and SIRT1 levels and protects the kidney from age-related AKI in an SIRT1-dependent manner. This study provides evidence suggesting that approaches to restore endogenous NAD+ levels are a potential therapeutic target for AKI, particularly in the elderly.


Salad Dressing: The Healthiest and Unhealthiest of Them All

When you think about salads, you immediately think it’s the best food option when you’re watching your weight. Since it’s made up of mostly greens, your mind labels it as the healthier choice. However, there are other factors that you have to take into consideration. Aside from the greens, what are the other ingredients in the salad? And most importantly, what is your salad dressing of choice?

That’s right, salad dressing plays a big part in making a meal healthy or not. Sure, you fill your plate with healthy green vegetables, but when you top it all off with a dollop of fatty and calorie-filled salad dressing, then your road to healthy eating is blocked right away. If you continue with choosing fatty salad dressing to accompany your salad, it will lead to a variety of health complications, such as overweight and obesity, heart troubles, diabetes, etc.

A salad a day is an important starting point toward a healthier life. Each additional serving further improves nutritional status. The greens you use in the salad provide calcium, potassium, iron, and B vitamins. In addition, these vegetables also have a healthy amount of dietary fiber, antioxidants to fight off harmful free radicals, and protein.

In the salad dressing world, there are basically two types of dressings: creamy and vinegar and oil (also called vinaigrettes). For the creamy dressings, some examples are blue cheese, ranch, thousand island, Caesar dressing. For the vinaigrettes, there are Italian dressing, balsamic vinaigrette, red wine vinaigrette, and Greek dressing.

Healthy Salad Dressing

Of course, the obvious healthier choice here is to go for the vinegar and oil–based salad dressings. And the healthiest way is to make your own at home. You can choose what kind of oil to use, and you can skip the added preservatives and sugars.

According to Mario Feruzzi, an associate professor of food science, salad dressing containing olive oil, canola oil, or another monounsaturated fat is ideal. This is because you will be able to get all the heart-healthy benefits of the vegetables you use in your salad without having too much fat. Monounsaturated fat best absorbs the most carotenoids from the vegetables you use in your salad.

The best kinds of vinegars to stock up on are balsamic, red wine, and white wine. They can be easily mixed with canola oil or olive oil.

The best oil to use is olive oil, especially virgin or extra-virgin olive oil. They have a huge amount of an antioxidant called polyphenols. Since they are naturally occurring and unhydrogenated, they don’t contain trans-fatty acids. These oils also have polyunsaturated or monounsaturated fats. These lower the LDL “bad” cholesterol levels. At the same time, it also increases HDL “good” cholesterol.

This type of salad dressing also improves the blood sugar levels of people with type 2 diabetes. This is because of the acetic acid in vinegar.

In addition this type of salad dressing paired with your salad will produce the effect of weight loss that you want. It only has a little bit of calories, it does not have refined sugar, and it keeps you feeling fuller longer.

Unhealthy Salad Dressing

That’s right, not everything in your salad is made up of nutritious elements. Most, if not all, of cream-based dressings can be pretty harmful to you. Creamy salad dressing usually have a base of mayonnaise, sour cream, or buttermilk. That means they are loaded with calories and unhealthy fat. In addition, they also have high levels of sodium and very little nutritional value. If you add in the factor that you buy them at the store, then you’re in for a super unhealthy meal.

Let’s discuss a few of the more famous creamy salad dressings.

Those that have “low fat” on their labels are doing you harm in other ways. These kinds of salad dressings usually have fillers and more added sugar to maintain the flavor without the fat.

The two main ingredients of ranch dressing, mayonnaise and sour cream, are dead giveaways of its unhealthiness. Just a quarter of a cup contains 220 calories and 22 grams of fat. In addition, it is high in sodium content as well, which is bad for people who suffer from heart disease or those with high blood pressure. Ouch. And you still have the gall to pour that over a supposedly healthy salad? Nope, I don’t think so.

Blue cheese salad dressing is loaded with calories. It has mayonnaise, sour cream, and blue cheese as the main ingredients, along with some other flavors. Also, it contains sodium, and eating too much sodium increases the risk of kidney damage, certain types of cancer, and heart disease.

Salad Dressing Recipes

Without a doubt, the one way you can ensure you are using the healthiest ingredients for your salad dressing is if you make them yourself. You get to choose what you use exactly. You can also customize the flavor and taste that you prefer.

Below are some super easy (and healthy!) salad dressing recipes you can make at home. Each recipe yields around ¼ cup of salad dressing. Take note that you can go ahead and experiment with other seasonings, oils, and flavored vinegars. Be sure to properly mix all the ingredients of each recipe. Also, remember to place each dressing in a tightly lidded container afterward. Give them around 10 minutes to stand alone in order for the dried herbs to rehydrate and for the flavors to properly blend. Enjoy!

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Based on the overwhelming
and positive response from‘
residents, a route was
designed to circulate from
public housing units and
eastside neighborhoods to
supermarkets and other
important community



Among the organizations represented on the FPC are grocery store chains,
community clinics, restaurants, a private think tank, the county legislature,
the Transportation Authority, religious groups, the Parks Department, and
community organizations. The Austin City Council and the Travis County
Legislature appoint the FPC’s 20 volunteer members. Soon after its
establishment, the FPC formed committees to execute a number of project
ideas. The new FPC received valuable outside assistance in 1995 when it
was chosen as one of four places to receive training as part of the Local
Food System Project (please see the Resource Guide).


Supermarket transportation. The FPC conducted a feasibility study to
assess the demand for a special direct bus route from east Austin to area
supermarkets. Based on the overwhelming and positive response from
residents, a route was designed to circulate from public housinghunits and
eastside neighborhoods to supermarkets and other important community
services. The FPC conducted a trial run of the route and coordinated
outreach, including a kick-off event, radio public service announcements,
and advertisements in community newspapers. The route, called the
Eastside Circulator, is still in service and very successful. Indeed, the Transit
Authority has asked the FPC to identify other communities in need of
improved transit services.

Community garden facilitation and fee waivers. While improving Eastside
residents’ capacity to grow their own food was a major goal of the FPC,
several local and state policies deterred the development of more
community gardens in low~—income neighborhoods. The most significant
obstacle was gaining access to water -— tap fees, capital recovery fees, and
hook-up fees for one lot would total over $5,000.

In addition, many eastside lots that might otherwise be suitable for
gardening had not been legally sub-divided and were thus ineligible for
water hook-up. (Four existing eastside gardens obtained their water
illegally from nearby sites.) The process of sub-division would cost an
additional $1,000 and take a year to complete. The FPC drew the city
council’s attention to these problems and the city council appointed a task
force to investigate.

In March 1996, the city council passed an ordinance defining community
gardens for the purpose of making such gardens eligible for water access
and exempt from high fees. In collaboration with the Parks and Recreation
Department, the Water and Wastewater Office of the Department of Public
Works, and a non-profit organization called Austin Community Gardens,
the FPC devised a simplified process that addressed most of the policy
barriers. Based on the need exhibited by east Austin residents, the FPC

Appendix B.


The FPC’s early successes show the value of conducting thorough research.
AQm provided compelling evidence to support its
recommendations; this helped convince policymakers and other key
stakeholders to address the issues rapidly and effectively. The research also
identified clear targets for food advocacy ~— transportation for food access
and community garden roadblocks — and described the issues thoroughly
enough to suggest solutions. These first two projects resulted in immediate,
tangible successes that secured continued commitment from FPC members
and caused a burst of visibility in the community. These projects also
exemplify the capacity of a food policy council to develop effective and
comprehensive policy.

The FPC has been unable to sustain a staff position, but SFC provides
staffing when possible. When funding is available, SFC employs a graduate
student as an intern. Kate Fitzgerald, in addition to leading the FPC,
allocates some of her own time to executing the projects the FPC develops.
Additional financial and technical support come from FPC members, each
of whom is required to commit $200 or an in-kind equivalent annually to
support FPC activities.

The FPC’s dependence on SFC for staff support can be a mixed blessing.
The availability of staff during the FPC’s first two years helped support two
well-planned and successful initiatives. However, when other projects
demand SFC’s resources, the FPC”s activities can fall into a lull. This
dependence is a common pitfall among food policy groups lacking a
securely funded staff position. Fortunately, Austin’s volunteer FPC


Succinate Explains Why Prebiotic Fiber Improves Blood Sugar Levels

Eating plenty of fiber is associated with multiple health benefits.

This is largely because fiber is resistant to human digestive enzymes and passes undigested down into the colon.

In the colon, gut bacteria ferment the fibers, producing beneficial byproducts such as short-chain fatty acids (SCFAs). Another less-known byproduct is succinate.

A recent study examined the health benefits of succinate in mice fed a high-fiber diet. Below is a summary of its findings, as well as some background information.


This article uses several terms that some readers may be unfamiliar with. Here are simple explanations.

Blood sugar control: Refers to the body’s ability to keep blood sugar levels stable and within healthy limits.

Intestinal gluconeogenesis (IGG): The formation of new glucose (sugar) by intestinal cells. IGG may improve blood sugar control by suppressing glucose production in the liver (1).

G6pc: A gene that is necessary for the production of new glucose in the body. Intestinal gluconeogensis cannot take place without it.

Prebiotic fiber: A type of fiber that promotes the growth of beneficial gut bacteria.

Fructo-oligosaccharides (FOS): A type of prebiotic fiber found in various fruits and vegetables. FOS are also sold as a dietary supplement.

Succinate: An organic acid (dicarboxylic acid) produced by certain gut bacteria when they are exposed to prebiotic fiber.

Prevotella copri: A type of gut bacteria that produces succinate from fiber.

Cecum: The mouse/rat equivalent of the human colon.

Article Reviewed

European researchers investigated the metabolic effects of succinate formation in the intestinal tracts of mice. This is the first study to focus on its health effects.

Microbiota-Produced Succinate Improves Glucose Homeostasis via Intestinal Gluconeogenesis.

Study Design

This series of interventional studies in mice tested the effects of a high-fiber or succinate-rich diet on blood sugar control.

To examine whether succinate leads to improved blood sugar control by initiating intestinal gluconeogensis (IGG), the researchers included two groups of mice:

  • Normal mice: This group included normal mice with all genes necessary for IGG.
  • G6pc-knockout mice: This group included intestinal-specific G6pc-knockout mice. Since they were lacking the G6pc gene, IGG did not take place.

In both groups, the mice were on a high-fat, high-sucrose diet. The experiment was further divided into two parts, depending on supplementation.

  • Prebiotic fiber: The diet was supplemented with fructo-oligosaccharides, a soluble, prebiotic fiber.
  • Succinate: The diet was supplemented with succinate.

Additionally, the study had two extensions. First, a separate part of the study examined the effects of a high-succinate diet on glucose formation in rat intestines.

Second, the researchers investigated the effects of supplementing with a type of bacteria known as Prevotella copri, which produces succinate.

Bottom Line: This series of interventional studies in mice and rats investigated the effects of succinate on blood sugar control.

Finding 1: A High-Fiber Diet Changed Gut Microbiota

Many previous studies clearly show that a diet high in prebiotic fiber affects gut microbiota — the types and relative abundance of bacteria living in the colon.

Additionally, studies show that a diet high in prebiotic fiber changes the gut microbiota in mice, irrespective of whether they are G6pc-knockout or not (2).

The current study supports earlier studies, showing that eating prebiotic fiber (fructo-oligosaccharides) significantly changed the gut microbiota in mice, regardless of whether they had the G6pc gene or not.

Specifically, prebiotic fiber increased the abundance of bacteria in the Bacteroidetesgroup, which includes Prevotella, relative to the Firmicutes group.

The Bacteroidetes group includes species of bacteria that are the major producers of succinate in the digestive tract (34).

Bottom Line: A diet high in prebiotic fiber significantly increased the abundance of bacteria that produce succinate.

Finding 2: Succinate Levels Increased on a High-Fiber Diet

Recent studies show that the levels of succinate in mouse cecum are elevated after eating fiber, and this increase is even more significant on a high-fat diet (567).

This is consistent with the present study’s findings. The researchers detected a significant increase in cecum succinate after a high-fat, high-sugar diet enriched with prebiotic fiber (fructo-oligosaccharides). This happened in both groups of mice.

Additionally, succinate levels rose higher than those of short-chain fatty acids, such as propionate and butyrate.

However, succinate levels were unchanged in the blood circulation, suggesting that most of it is metabolized in the intestines.

Bottom Line: A diet high in prebiotic fiber significantly increased the levels of succinate in mouse cecum (colon).

Finding 3: Succinate Improved Blood Sugar Control

The researchers discovered that when rats were fed succinate, it was converted into glucose by intestinal cells.

This process is known as intestinal gluconeogenesis (IGG). Some scientists consider IGG to be a key regulator of the body’s energy balance (28).

Contrary to what you might think, studies show that IGG actually improves blood sugar control (19).

The present results are in agreement with previous findings. The study showed that succinate reduced blood sugar and insulin levels by suppressing glucose production in the liver.

However, succinate only improved blood sugar control in the normal mice, whereas the G6pc-knockout mice experienced no benefits.

These findings are consistent with studies showing that mice lacking the G6pc gene, which is necessary for IGG, did not benefit from a diet high in prebiotic fiber (fructo-oligosaccharides) (2).

Taken together, the results suggest that prebiotic fiber and succinate improve blood sugar control through their effects on IGG.

Bottom Line: Supplementing with succinate significantly improved blood sugar control by stimulating intestinal gluconeogenesis.

Finding 4: Prevotella copri Increased Succinate Levels and Improved Blood Sugar Control

Several types of bacteria produce succinate when exposed to dietary fiber.

These include bacteria of the Prevotella group, most notably Prevotella copri, which is found in the human digestive tract (10).

The present study tested the effects of supplementing the diet of mice with a live culture of P. copri.

The researchers found that supplementing with P. copri significantly increased blood sugar control (glucose tolerance), an effect that was linked with a reduction in liver glucose production.

These findings are in agreement with a previous study showing that a high abundance of P. copri was associated with improved blood sugar control in healthy people (11).

Interestingly, P. copri benefited both the normal mice and the G6pc-knockout mice, indicating that P. copri has additional, succinate-independent benefits on blood sugar control.

Bottom Line: Supplementing with Prevotella copri, a type of succinate-producing bacteria, improved blood sugar control, irrespective of intestinal gluconeogenesis.


Since this was a series of studies in mice and rats, the findings do not necessarily apply to humans.

Although basic metabolism is similar in rodents and humans, randomized controlled trials are needed to confirm the health effects of succinate in people.

Summary and Real-Life Application

In short, this series of studies in rats and mice suggests the following:

  • Prebiotic fiber (fructo-oligosaccharides) increases the abundance of gut bacteria that produce succinate.
  • A diet high in prebiotic fiber increases succinate levels in the digestive tract.
  • Supplementing with succinate improves blood sugar control.
  • Succinate is converted to glucose by intestinal cells, a process known as intestinal gluconeogenesis (IGG).
  • IGG improves blood sugar control by inhibiting liver gluconeogenesis.
  • Mice that do not have the gene (G6pc) necessary for IGG do not benefit from supplementing with fructo-oligosaccharides or succinate.
  • Supplementing with Prevotella copri, a succinate-producing bacteria, improves blood-sugar control in normal and G6pc-knockout mice, suggesting that it may have succinate-independent benefits.

Succinate may have similar benefits in humans. However, randomized controlled trials in people are needed before any strong conclusions can be reached.