Time Course for Fasting-induced Autophagy in Humans

August 23, 2022 updated by: Montefiore Medical Center
Autophagy, which involves the degradation of aged or damaged cellular components, has been shown to extend healthspan and lifespan in multiple organisms, including flies, worms, and mice. Research has also demonstrated that autophagy declines with age in these simpler experimental models. However, human studies are lacking. Our study seeks to determine whether fasting, a robust stimulus of autophagy, upregulates autophagy in humans, and whether autophagy is reduced in healthy older people compared to healthy younger individuals.

Study Overview

Status

Withdrawn

Intervention / Treatment

Detailed Description

Autophagy is a cellular quality control pathway that degrades aged or damaged organelles and protein aggregates within lysosomes. By doing so, autophagy provides an alternate source of energy for cells to cope with adverse conditions. The level of autophagy determines the degree to which aged cells are able to eliminate damaged organelles and/or toxic aggregates and mount a protective response against stress. At the physiological level, nutrient deprivation or fasting is one of the most robust stimuli for autophagy across diverse experimental systems.1 Our lab has shown important roles for autophagy in lipid/glucose homeostasis and regulation of energy balance. We have found that autophagy degrades cellular lipid stores via a process we described as lipophagy. We have also shown contributions of autophagy to the regulation of feeding as well as its developmental roles in maintenance of muscle and fat mass. In addition to these physiological functions, a number of studies have revealed that mice lacking autophagy in the central nervous system show rapid onset of neurodegeneration and an early death.2,3 These studies support a central role of autophagy in the maintenance of healthspan.

It is well-established that autophagy activity declines with age, which has led to the hypothesis that autophagy failure contributes to the metabolic syndrome of aging. In fact, young mice with tissue-specific knockout of the autophagy gene Atg7 display features of aging, including loss of muscle mass (mimicking sarcopenia of aging), fatty liver, decreased adipose lipolysis, de-differentiation of brown fat, and pancreatic β-cell dysfunction.4-6 Conversely, restoration of autophagy via pharmacological or genetic approaches prevents age-associated decline in cell function and improves stress response-thus directly extending healthspan. As a consequence, there is great interest in developing new experimental approaches to prevent age-associated chronic diseases. In fact, caloric restriction (CR) has been shown to stimulate autophagy and extend lifespan and healthspan in multiple experimental models. While these CR studies were carried out in simpler organisms, such as flies, worms, and mice,7-9 similar studies in humans are largely lacking. Since autophagy is activated by starvation, the prevailing hypothesis is that caloric restriction (CR) or more physiological approaches such as intermittent fasting will stimulate autophagy in humans, which in turn will prevent or retard the onset of age-associated chronic diseases. There is limited knowledge if indeed extended periods of fasting will activate autophagy in humans. In addition, we do not know what duration of fasting may be required to stimulate autophagy in humans. Finally, we do not know if, nor by how much, fasting-induced autophagy is reduced in aging humans. Due to the aforementioned gaps in our knowledge regarding autophagy in humans, in this study we will test the ability of extended periods of restriction to food to stimulate autophagy in healthy, young individuals. Further, we will compare the extent to which autophagy is reduced in healthy older subjects, when compared to those observed in young controls. In our study, we will be using samples of adipose tissue, a metabolically active endocrine organ, and peripheral blood cells, which have both been evaluated in prior autophagy studies and can be obtained in a less invasive manner.

Study Type

Interventional

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

    • New York
      • Bronx, New York, United States, 10461
        • Albert Einstein College Of Medicine

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 85 years (ADULT, OLDER_ADULT)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Healthy men and women 18-35 years of age
  • Healthy men and women 65-85 years of age

Exclusion Criteria:

  • Serious acute/chronic illness (e.g., active cancer, inflammatory states, RA, SLE, or a CVD event within past 6 months)
  • Diabetes or pre-diabetes with an A1c >6.0%
  • Pregnancy
  • BMI >30 kg/m2 or <20 kg/m2
  • eGFR <45 ml/min
  • ALT >3x ULN
  • Hct <35 or Hb <10
  • Exclusionary meds: calcium channel blockers, anticonvulsants or other drugs shown to affect autophagy (see table below)
  • Food allergy or known food intolerance
  • Active Smoking (>1 cigarette or cigar per week)
  • Use of recreational drugs (opioids, cocaine, marijuana, etc.) in past month
  • Use of alcohol on the day prior to and the day of study
  • Shift workers or other dysregulated sleep pattern (habitual use of sleep medications, jet lag, etc.)
  • Strenuous exercise within 3 days prior to study visit 2
  • Any condition the investigator believes would impair the ability to interpret targeted outcomes

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: BASIC_SCIENCE
  • Allocation: NON_RANDOMIZED
  • Interventional Model: PARALLEL
  • Masking: NONE

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
EXPERIMENTAL: Young
10 healthy men and women 18-35 yo.
23 hours fasting
ACTIVE_COMPARATOR: Older adults
10 healthy men and women 65-85 yo
23 hours fasting

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Autophagy flux
Time Frame: 23 hours
The turnover rate of the autophagosome marker LC3-II will be assessed. LC3-II flux will be performed in freshly isolated fat tissues and in PBMCs at various timepoints. Freshly collected fat tissue explants and PBMCs will be incubated in dishes with high-glucose culture medium (DMEM) in the presence or absence of lysosomal inhibitors (Lys Inh), leupeptin (200uM) and ammonium chloride (20uM) at 37°C, 5% CO2 for 4 hours. Fat explants and scraped PMBC pellets will then be homogenized in a buffer containing protease and phosphatase inhibitors and subjected to immunoblotting for LC3. Autophagy flux will be determined by subtracting the densitometric value of LC3-II in Lys Inh-untreated samples from the Lys Inh-treated samples.
23 hours

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Level of ketone bodies
Time Frame: 23 hours
Levels of ketones in the plasma will be assessed with blood draws at various timepoints.
23 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Investigators

  • Principal Investigator: Rajat Singh, MD, Albert Einstein College Of Medicine

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (ACTUAL)

November 19, 2021

Primary Completion (ANTICIPATED)

May 31, 2022

Study Completion (ANTICIPATED)

February 1, 2023

Study Registration Dates

First Submitted

April 6, 2021

First Submitted That Met QC Criteria

April 9, 2021

First Posted (ACTUAL)

April 13, 2021

Study Record Updates

Last Update Posted (ACTUAL)

August 26, 2022

Last Update Submitted That Met QC Criteria

August 23, 2022

Last Verified

August 1, 2022

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2021-12857

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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